| isolation, reconstitution and functional characterisation of the rhodobacter sphaeroides photoactive yellow protein. | we report the isolation, functional reconstitution and photophysical characterisation of rhodobacter sphaeroides photoactive yellow protein (pyp), of which the gene was recently cloned. reconstitution of the his-tagged purified apo-protein with 4-hydroxy-cinnamic acid yields the characteristic blue absorbance at 446 nm, but surprisingly also an absorbance peak at 360 nm. this additional peak is not caused by binding of a second chromophore, as confirmed with mass spectroscopy. moreover, reconsti ... | 2000 | 11108842 |
| gene disruption analysis of dppa isolated as a periplasmic molecular chaperone-like protein for folding of dimethyl sulfoxide reductase in rhodobacter sphaeroides f. sp. denitrificans. | the effect of inactivation of dppa, a dipeptide transport protein identified as a periplasmic molecular chaperone-like protein, on the formation of active dimethyl sulfoxide reductase (dmsor) was examined in rhodobacter sphaeroides f. sp. denitrificans. all of the dppa-disrupted mutants produced a normal level of native form of dmsor and grew by dmso respiration, indicating that the loss of dppa protein alone had no effect on the formation of active dmsor. the periplasmic fraction of the dppa-di ... | 2000 | 11111028 |
| genetic structure and functional implication of the fcb gene cluster for hydrolytic dechlorination of 4-chlorobenzoate from pseudomonas sp. dj-12. | the fcb gene cluster responsible for the hydrolytic dechlorination of 4-chlorobenzoate (4cba) was cloned from the chromosomal dna of pseudomonas sp. dj-12, and its nucleotide sequence analyzed. the gene cluster was organized in the order fcbb-fcba-fcbt1-fcbt2-cbt3-fcbc, which is different from that reported in other bacteria. a promoter-like sequence (-35 and -10 region) is located upstream of the fcbb gene and putative ribosome-binding sequences were found upstream of the respective orfs. a ste ... | 2000 | 11111048 |
| probing the role of the fe-s subunit hinge region during q(o) site catalysis in rhodobacter capsulatus bc(1) complex. | the ubihydroquinone:cytochrome c oxidoreductase, or bc(1) complex, functions according to a mechanism known as the modified q cycle. recent crystallographic data have revealed that the extrinsic domain containing the [2fe2s] cluster of the fe-s subunit of this enzyme occupies different positions in various crystal forms, suggesting that this subunit may move during ubihydroquinone oxidation. as in these structures the hydrophobic membrane anchor of the fe-s subunit remains at the same position, ... | 2000 | 11112533 |
| proteolytic cleavage of the fe-s subunit hinge region of rhodobacter capsulatus bc(1) complex: effects of inhibitors and mutations. | the three-dimensional structure of the mitochondrial bc(1) complex reveals that the extrinsic domain of the fe-s subunit, which carries the redox-active [2fe2s] cluster, is attached to its transmembrane anchor domain by a short flexible hinge sequence (amino acids d43 to s49 in rhodobacter capsulatus). in various structures, this extrinsic domain is located in different positions, and the conformation of the hinge region is different. in addition, proteolysis of this region has been observed pre ... | 2000 | 11112534 |
| 1-deoxy-d-xylulose 5-phosphate synthase, the gene product of open reading frame (orf) 2816 and orf 2895 in rhodobacter capsulatus. | in eubacteria, green algae, and plant chloroplasts, isopentenyl diphosphate, a key intermediate in the biosynthesis of isoprenoids, is synthesized by the methylerythritol phosphate pathway. the five carbons of the basic isoprenoid unit are assembled by joining pyruvate and d-glyceraldehyde 3-phosphate. the reaction is catalyzed by the thiamine diphosphate-dependent enzyme 1-deoxy-d-xylulose 5-phosphate synthase. in rhodobacter capsulatus, two open reading frames (orfs) carry the genes that encod ... | 2001 | 11114895 |
| redesign of the proton-pumping machinery of cytochrome c oxidase: proton pumping does not require glu(i-286). | one of the putative proton-transfer pathways leading from solution toward the binuclear center in many cytochrome c oxidases is the d-pathway, so-called because it starts with a highly conserved aspartate [d(i-132)] residue. another highly conserved amino acid residue in this pathway, glutamate(i-286), has been indicated to play a central role in the proton-pumping machinery of mitochondrial-type enzymes, a role that requires a movement of the side chain between two distinct positions. in the pr ... | 2000 | 11123910 |
| modeling the bacterial photosynthetic reaction center 3: interpretation of effects of site-directed mutagenesis on the special-pair midpoint potential. | interpretation of changes in midpoint potential of the "special pair" in bacterial photosynthetic reaction centers caused by site-directed mutagenesis is discussed in terms of a simple tight-binding model which relates them to concomitant variations in spin distribution between the two bacteriochlorophyll molecules of the special pair. our analysis improves on previous similar ones by allen and co-workers [artz, k., williams, j. c., allen, j. p., lendzian, f., rautter, j., and lubitz, w. (1997) ... | 2000 | 11123947 |
| dccd inhibits the reactions of the iron-sulfur protein in rhodobacter sphaeroides chromatophores. | n,n'-dicyclohexylcarbodiimide (dccd) has been reported to inhibit proton translocation by cytochrome bc(1) and b(6)f complexes without significantly altering the rate of electron transport, a process referred to as decoupling. to understand the possible role of dccd in inhibiting the protonogenic reactions of cytochrome bc(1) complex, we investigated the effect of dccd modification on flash-induced electron transport and electrochromic bandshift of carotenoids in rb. sphaeroides chromatophores. ... | 2000 | 11123950 |
| interactions between the donor and acceptor sides in bacterial reaction centers. | the apparent equilibrium constant k'(2) for electron transfer between the primary (q(a)) and secondary (q(b)) quinone acceptors of the reaction center was measured in chromatophores of rhodobacter capsulatus. in the presence of the oxidized primary donor p(+), we obtained a value of k'(2)(p(+)) approximately 100 at ph 7.2, based on the rates of recombination from p(+)q(a-) and p(+)q(b-). k'(2) was also measured in the presence of reduced p, from the damping of semiquinone oscillations during a s ... | 2000 | 11123956 |
| electron-transfer supercomplexes in photosynthesis and respiration. | | 2000 | 11126443 |
| how carotenoids protect bacterial photosynthesis. | the essential function of carotenoids in photosynthesis is to act as photoprotective agents, preventing chlorophylls and bacteriochlorophylls from sensitizing harmful photodestructive reactions in the presence of oxygen. based upon recent structural studies on reaction centres and antenna complexes from purple photosynthetic bacteria, the detailed organization of the carotenoids is described. then with specific reference to bacterial antenna complexes the details of the photoprotective role, tri ... | 2000 | 11127989 |
| evidence for a functional similarity between the two-component regulatory systems regsr, actsr, and regba (prrba) in alpha-proteobacteria. | the symbiotic bacteria bradyrhizobium japonicum and sinorhizobium meliloti, and the purple photosynthetic bacteria rhodobacter capsulatus, rhodovulum sulfidophilum, roseobacter denitrificans and rhodobacter sphaeroides possess homologous two-component regulatory systems, namely regsr, actsr, regba and prrba. the respective response regulators of these bacteria control expression of different regulons that are involved in n2 fixation, co2 fixation, photosynthesis or acid tolerance. we therefore a ... | 2000 | 11131020 |
| maintenance and control of redox poise in rhodobacter capsulatus strains deficient in the calvin-benson-bassham pathway. | carbon dioxide serves as the preferred electron acceptor during photoheterotrophic growth of nonsulfur purple photosynthetic bacteria such as rhodobacter capsulatus and rhodobacter sphaeroides. this co2, produced as a result of the oxidation of preferred organic carbon sources, is reduced through reactions of the calvin-benson-bassham reductive pentose phosphate pathway. this pathway is thus crucial to maintain a balanced intracellular oxidation-reduction potential (or redox poise) under photohe ... | 2000 | 11131022 |
| urea utilization in the phototrophic bacterium rhodobacter capsulatus is regulated by the transcriptional activator ntrc. | the phototrophic nonsulfur purple bacterium rhodobacter capsulatus can use urea as a sole source of nitrogen. three transposon tn5-induced mutations (xan-9, xan-10, and xan-19), which led to a ure(-) phenotype, were mapped to the uref and urec genes, whereas two other tn5 insertions (xan-20 and xan-22) were located within the ntrc and ntrb genes, respectively. as in klebsiella aerogenes and other bacteria, the genes encoding urease (ureabc) and the genes required for assembly of the nickel metal ... | 2001 | 11133958 |
| primary alcohols and di-alcohols as growth substrates for the purple nonsulfur bacterium rhodobacter capsulatus. | growth experiments were performed with the purple nonsulfur bacterium rhodobacter capsulatus to test its ability to use aliphatic, methyl-substituted, and unsaturated alcohols, as well as di-alcohols, as carbon sources for growth. both phototrophic and chemotrophic growth was observed on a wide variety of such alcohols. by contrast, secondary or tertiary alcohols, or primary alcohols containing an ethyl or propyl substituent, did not support growth. in addition, preculture history and serial sub ... | 2000 | 11142409 |
| effect of metal binding on electrogenic proton transfer associated with reduction of the secondary electron acceptor (qb) in rhodobacter sphaeroides chromatophores. | the influence of metal ion (cd(2+), zn(2+), ni(2+)) binding on the electrogenic phases of proton transfer connected with reduction of quinone q(b) in chromatophores from rhodobacter sphaeroides was studied by time-resolved electric potential changes. in the presence of metals, the electrogenic transients associated with proton transfer on first and second flash at ph 8 were found to be slower by factors of 3-6. this is essentially the same effect of metal binding that was observed on optical tra ... | 2001 | 11148037 |
| active site heterogeneity in dimethyl sulfoxide reductase from rhodobacter capsulatus revealed by raman spectroscopy. | raman spectroscopy has been used to investigate the structure of the molybdenum cofactor in dmso reductase from rhodobacter capsulatus. three oxidized forms of the enzyme, designated 'redox cycled', 'as prepared', and dmsor(mod)d, have been studied using 752 nm laser excitation. in addition, two reduced forms of dmso reductase, prepared either anaerobically using dms or using dithionite, have been characterized. the 'redox cycled' form has a single band in the mo=o stretching region at 865 cm(-1 ... | 2001 | 11148038 |
| fusion of chromatophores from photosynthetic bacteria with a supported lipid layer: characterization of the electric units. | direct electrometric measurements of membrane potential changes are a valuable tool for study of vectorial transfer of electrons, protons, and ions. commonly model membrane systems are created by fusion of lipid/protein vesicles with lipid-coated thin films. we characterized the electric units resulting from this process using chromatophores from the purple bacterium rhodobacter sphaeroides and either a mylar film or a planar modified gold electrode as support. investigation of the shunting acti ... | 2000 | 11150512 |
| topological analysis of dctq, the small integral membrane protein of the c4-dicarboxylate trap transporter of rhodobacter capsulatus. | tripartite atp-independent periplasmic ('trap') transporters are a novel group of bacterial and archaeal secondary solute uptake systems which possess a periplasmic binding protein, but which are unrelated to atp-binding cassette (abc) systems. in addition to the binding protein, trap transporters contain two integral membrane proteins or domains, one of which is 40-50 kda with 12 predicted transmembrane (tm) helices, thought to be the solute import protein, while the other is 20-30 kda and of u ... | 2001 | 11150659 |
| steady-state cyclic electron transfer through solubilized rhodobacter sphaeroides reaction centres. | the mechanism, thermodynamics and kinetics of light-induced cyclic electron transfer have been studied in a model energy-transducing system consisting of solubilized rhodobacter sphaeroides reaction center/light harvesting-1 complexes (so-called core complexes), horse heart cytochrome c and a ubiquinone-0/ubiquinol-0 pool. an analysis of the steady-state kinetics of cytochrome c reduction by ubiquinol-0, after a light-induced steady-state electron flow had been attained, showed that the rate of ... | 2000 | 11152271 |
| a simple approach to membrane protein secondary structure and topology based on nmr spectroscopy. | this paper describes a simple, qualitative approach for the determination of membrane protein secondary structure and topology in lipid bilayer membranes. the approach is based on the observation of wheel-like resonance patterns observed in the nmr 1h-15n/15n polarization inversion with spin exchange at the magic angle (pisema) and 1h/15n heteronuclear correlation (hetcor) spectra of membrane proteins in oriented lipid bilayers. these patterns, named pisa wheels, have been previously shown to re ... | 2001 | 11159466 |
| control of hema expression in rhodobacter sphaeroides 2.4.1: effect of a transposon insertion in the hbda gene. | the common precursor to all tetrapyrroles is 5-aminolevulinic acid (ala), and in rhodobacter sphaeroides its formation occurs via the shemin pathway. ala synthase activity is encoded by two differentially regulated genes in r. sphaeroides 2.4.1: hema and hemt. in our investigations of hema regulation, we applied transposon mutagenesis under aerobic conditions, followed by a selection that identified transposon insertion mutants in which hema expression is elevated. one of these mutants has been ... | 2001 | 11160087 |
| the hook gene (flge) is expressed from the flgbcdef operon in rhodobacter sphaeroides: study of an flge mutant. | in this work we identified the flge gene encoding the flagellar hook protein from rhodobacter sphaeroides. our results show that this gene is part of a flagellar cluster that includes the genes flgb, flgc, flgd, flge, and flgf. two different types of mutants in the flge gene were isolated, and both showed a fla(-) phenotype, indicating the functionality of this sequence. complementation studies of these mutant strains suggest that flge is included in a single transcriptional unit that starts in ... | 2001 | 11160099 |
| role for dratg and rnf genes in reduction of 2,4-dinitrophenol by rhodobacter capsulatus. | the phototrophic bacterium rhodobacter capsulatus is able to reduce 2,4-dinitrophenol (dnp) to 2-amino-4-nitrophenol enzymatically and thus can grow in the presence of this uncoupler. dnp reduction was switched off by glutamine or ammonium, but this short-term regulation did not take place in a dratg deletion mutant. nevertheless, the target of dratg does not seem to be the nitrophenol reductase itself since the ammonium shock did not inactivate the enzyme. in addition to this short-term regulat ... | 2001 | 11160111 |
| protein control of the redox potential of the primary quinone acceptor in reactionccenters from rhodobacter sphaeroides. | the role of the protein environment in determining the redox midpoint potential (e(m)) of q(a), the primary quinone of bacterial reaction centers, was investigated by mutation of isoleucine at position 265 of the m subunit in rhodobacter sphaeroides. isoleucine was changed to threonine, serine, and valine, yielding mutants m265it, m265is, and m265iv, respectively. all three mutants, with smaller residues replacing isoleucine, exhibited decreased binding affinities of the q(a) site for various qu ... | 2001 | 11170424 |
| kinetic and mechanistic properties of biotin sulfoxide reductase. | rhodobacter sphaeroides f. sp. denitrificans biotin sulfoxide reductase catalyzes the reduction of d-biotin d-sulfoxide (bso) to biotin. initial rate studies of the homogeneous recombinant enzyme, expressed in escherichia coli, have demonstrated that the purified protein utilizes nadph as a facile electron donor in the absence of any additional auxiliary proteins. we have previously shown [pollock, v. v., and barber, m. j. (1997) j. biol. chem. 272, 3355-3362] that, at ph 8 and in the presence o ... | 2001 | 11170471 |
| crystallization and preliminary x-ray diffraction analysis of a [2fe-2s] ferredoxin (fdvi) from rhodobacter capsulatus. | a [2fe-2s] ferredoxin found in the photosynthetic bacterium rhodobacter capsulatus has been purified in recombinant form from escherichia coli. this protein, called fdvi, resembles ferredoxins involved in iron-sulfur cluster biosynthesis in various prokaryotic and eukaryotic cells. purified recombinant fdvi was recovered in high yields and appeared to be indistinguishable from the genuine r. capsulatus ferredoxin based on uv-visible absorption and epr spectroscopy and mass spectrometry. fdvi has ... | 2001 | 11173487 |
| pumping capacity of bacterial reaction centers and backpressure regulation of energy transduction. | transduction of free-energy by rhodobacter sphaeroides reaction-center-light-harvesting-complex-1 (rclh1) was quantified. rclh1 complexes were reconstituted into liposomal membranes. the capacity of the rclh1 complex to build up a proton motive force was examined at a range of incident light intensities, and induced proton permeabilities, in the presence of artificial electron donors and acceptors. experiments were also performed with rclh1 complexes in which the midpoint potential of the reacti ... | 2001 | 11179962 |
| mutations of the helicobacter pylori genes rdxa and pbp1 cause resistance against metronidazole and amoxicillin. | to investigate amoxicillin and metronidazole resistance of helicobacter pylori, we compared putative resistance genes between resistant strains obtained in vitro and their sensitive parent strain. all metronidazole-resistant strains had rdxa mutations, and an amoxicillin-resistant strain had pbp1 and pbp2 mutations. by transforming pcr products of these mutated genes into antibiotic-sensitive strains, we showed that rdxa null mutations were sufficient for metronidazole resistance, while pbp1 mut ... | 2001 | 11181392 |
| electron transfer. exploiting thermal motion. | | 2000 | 11183149 |
| reaction centres of purple bacteria. | the bacterial reaction centre is undoubtedly one of the most heavily studied electron transfer proteins and, as this article has tried to describe, it has made some unique contributions to our understanding of biological electron transfer and coupled protonation reactions, and has provided fascinating information in areas that concern basic properties such as protein heterogeneity and protein dynamics. despite intensive study, much remains to be learned about how this protein catalyses the conve ... | 2000 | 11192735 |
| acceleration of the recombination reaction between photooxidized bacteriochlorophyll and reduced primary quinone in reaction centers of rhodobacter sphaeroides at t > 300 k. | | 2000 | 11216460 |
| photosynthetic electron transfer controlled by protein relaxation: analysis by langevin stochastic approach. | relaxation processes in proteins range in time from picoseconds to seconds. correspondingly, biological electron transfer (et) could be controlled by slow protein relaxation. we used the langevin stochastic approach to describe this type of et dynamics. two different types of kinetic behavior were revealed, namely: oscillating et (that could occur at picoseconds) and monotonically relaxing et. on a longer time scale, the et dynamics can include two different kinetic components. the faster one re ... | 2001 | 11222272 |
| is there a conserved interaction between cardiolipin and the type ii bacterial reaction center? | in a recent publication, the structural details of an interaction between the rhodobacter sphaeroides reaction center and the anionic phospholipid diphosphatidyl glycerol (cardiolipin) were described (k. e. mcauley, p. k. fyfe, j. p. ridge, n. w. isaacs, r. j. cogdell, and m. r. jones, 1999, proc. natl. acad. sci. u.s.a. 96:14706-14711). this was the first crystallographic description of an interaction between this biologically important lipid and an integral membrane protein and was also the fi ... | 2001 | 11222300 |
| effect of high pressure on the photochemical reaction center from rhodobacter sphaeroides r26.1. | high-pressure studies on the photochemical reaction center from the photosynthetic bacterium rhodobacter sphaeroides, strain r26.1, shows that, up to 0.6 gpa, this carotenoid-less membrane protein does not loose its three-dimensional structure at room temperature. however, as evidenced by fourier-transform preresonance raman and electronic absorption spectra, between the atmospheric pressure and 0.2 gpa, the structure of the bacterial reaction center experiences a number of local reorganizations ... | 2001 | 11222309 |
| mobile cytochrome c2 and membrane-anchored cytochrome cy are both efficient electron donors to the cbb3- and aa3-type cytochrome c oxidases during respiratory growth of rhodobacter sphaeroides. | we have recently established that the facultative phototrophic bacterium rhodobacter sphaeroides, like the closely related rhodobacter capsulatus species, contains both the previously characterized mobile electron carrier cytochrome c2 (cyt c2) and the more recently discovered membrane-anchored cyt cy. however, r. sphaeroides cyt cy, unlike that of r. capsulatus, is unable to function as an efficient electron carrier between the photochemical reaction center and the cyt bc1 complex during photos ... | 2001 | 11222600 |
| effects of extraction of the h-subunit from rhodobacter sphaeroides reaction centers on relaxation processes associated with charge separation. | effects of extraction of the h-subunit from rhodobacter sphaeroides photosynthetic reaction centers (rc) on the characteristics of the photoinduced conformational transition associated with electron transfer between photoactive bacteriochlorophyll and primary quinone acceptor were studied. extraction of the h-subunit (i.e., the subunit that is not directly bound to electron transfer cofactors) was found to have a significant effect on the dynamic properties of the protein--pigment complex of the ... | 2001 | 11240399 |
| evidence for a quinone binding site close to the interface between nuod and nuob subunits of complex i. | piericidin, rotenone and pyridaben are specific inhibitors of the nadh-ubiquinone oxidoreductase (complex i) that bind to its ubiquinone binding site(s). using site directed mutagenesis, we demonstrate that residues g409, d412, r413 and v407 of the c-terminus of complex i nuod subunit are directly involved in the binding of these inhibitors. we propose that the corresponding inhibitor/quinone binding site would be located close to nuod-nuob interface. | 2001 | 11245783 |
| long-lived charge-separated states in bacterial reaction centers isolated from rhodobacter sphaeroides. | we studied the accumulation of long-lived charge-separated states in reaction centers isolated from rhodobacter sphaeroides, using continuous illumination, or trains of single-turnover flashes. we found that under both conditions a long-lived state was produced with a quantum yield of about 1%. this long-lived species resembles the normal p(+)q(-) state in all respects, but has a lifetime of several minutes. under continuous illumination the long-lived state can be accumulated, leading to close ... | 2001 | 11245794 |
| transmembrane orientation and topology of the nadh:quinone oxidoreductase putative quinone binding subunit nuoh. | nadh:quinone oxidoreductase, or complex i, is a multi-subunit membrane-bound enzyme in the respiratory chain of many pro- and eukaryotes. the enzyme catalyzes the oxidation of nadh and donates electrons to the quinone pool, coupled to proton translocation across the membrane, but the mechanism of energy transduction is not understood. in bacteria the enzyme consists of 14 subunits, seven membrane spanning and seven protruding from the membrane. the hydrophobic nuoh (nqo8, nd1, nad1, ndha) subuni ... | 2001 | 11245799 |
| generalized approach to the regulation and integration of gene expression. | the volume of electron flow through the cbb3 branch of the electron transport chain and the redox state of the quinone pool generate signals that regulate photosynthesis gene expression in rhodobacter sphaeroides. an inhibitory signal is generated at the level of the catalytic subunit of the cbb3 cytochrome c oxidase and is transduced through the membrane-localized prrc polypeptide to the prrba two-component activation system, which controls the expression of most of the photosynthesis genes in ... | 2001 | 11251830 |
| molecular evolution of the amp-forming acetyl-coa synthetase. | acetyl-coa-synthetase (acs) is involved in the production of acetate, a major metabolite in numerous organisms. there are two forms of this enzyme: adp-forming acs and atp-forming acs. we focus mainly on the amp-forming acs gene, which is relatively well conserved in eubacteria, archeaebacteria, and eukaryotes. blast searches in databases showed 30 protein sequences significantly related to the acs. most of these sequences were identified as acs but three of them, belonging to the mammalian spec ... | 2001 | 11255012 |
| charge separation in photosynthetic reaction centers under femtosecond excitation. | the process of electron transfer from the primary electron donor p* to the primary electron acceptor ba in the reaction center of rhodobacter sphaeroides r-26 under 30 fsec pulse excitation was studied in this work with the aim of establishing a relationship between the nuclear subsystem motion and charge transfer. for this purpose the fsec and psec oscillations in the bands of stimulated emission of p* and in the band of reaction product ba- at 1020 nm were investigated. it was established that ... | 2001 | 11255130 |
| absorption changes induced by the binding of triazines to the qb pocket in reaction centers of rhodobacter capsulatus. | inhibitors which block electron transfer from the primary (q(a)) to the secondary (q(b)) quinone of the bacterial reaction center are competing with the pool ubiquinones for binding at the q(b) pocket. due to the much greater stability of the semiquinone state q(b)(-) compared with fully oxidized or reduced quinone, a displacement of the inhibitors takes place after one flash from state q(a)(-)i to state q(a)q(b)(-). this process can be monitored from near-ir absorption changes which reflect loc ... | 2001 | 11258912 |
| trapping conformational intermediate states in the reaction center protein from photosynthetic bacteria. | in protein, conformational changes are often crucial for function but not easy to observe. two functionally relevant conformational intermediate states of photosynthetic reaction center protein (rcs) are trapped and characterized at low temperature. rcs frozen in the dark do not allow electron transfer from the reduced primary quinone, q(a)(-), to the secondary quinone, q(b). in contrast, rcs frozen under illumination in the product (p(+)q(a)q(b)(-)) state, with the oxidized electron donor, p(+) ... | 2001 | 11258940 |
| molecular organization of the ribosomal rna transcription unit and the phylogenetic study of zymomonas mobilis zm4. | previously we reported that zymomonas mobilis zm4 contains three ribosomal transcription units (rrna to c operons) which are clustered around the 50 min region, paci fragments 13 and 6, on the physical map of z. mobilis zm4 [kang, h. l. and kang, h. s. (1998) gene 206, 223-228]. the physical map reveals that the rrna gene set is located on the 76 kb paci fragment 13. the complete nucleotide sequence of the rrna gene set has been determined. the total number of nucleotides of the rrna gene set is ... | 2001 | 11266123 |
| femo cofactor biosynthesis in a nife- mutant of rhodobacter capsulatus. | in all diazotrophic micro-organisms investigated so far, mutations in nife, one of the genes involved in the biosynthesis of the femo cofactor (femoco), resulted in the accumulation of cofactorless inactive dinitrogenase. in this study, we have found that strains of the phototrophic non-sulfur purple bacterium rhodobacter capsulatus with mutations in nife, as well as in the operon harbouring the nife gene, were capable of reducing acetylene and growing diazotrophically, although at distinctly lo ... | 2001 | 11277916 |
| an active site tyrosine influences the ability of the dimethyl sulfoxide reductase family of molybdopterin enzymes to reduce s-oxides. | dimethyl sulfoxide reductase (dmsor), trimethylamine-n-oxide reductase (tmaor), and biotin sulfoxide reductase (bsor) are members of a class of bacterial oxotransferases that contain the bis(molybdopterin guanine dinucleotide)molybdenum cofactor. the presence of a tyr residue in the active site of dmsor and bsor that is missing in tmaor has been implicated in the inability of tmaor, unlike dmsor and bsor, to utilize s-oxides. to test this hypothesis, escherichia coli tmaor was cloned and express ... | 2001 | 11278798 |
| x-ray structure analyses of photosynthetic reaction center variants from rhodobacter sphaeroides: structural changes induced by point mutations at position l209 modulate electron and proton transfer. | the structures of the reaction center variants pro l209 --> tyr, pro l209 --> phe, and pro l209 --> glu from the photosynthetic purple bacterium rhodobacter sphaeroides have been determined by x-ray crystallography to 2.6-2.8 a resolution. these variants were constructed to interrupt a chain of tightly bound water molecules that was assumed to facilitate proton transfer from the cytoplasm to the secondary quinone q(b) [baciou, l., and michel, h. (1995) biochemistry 34, 7967-7972]. however, the a ... | 2001 | 11284681 |
| on the role of the k-proton transfer pathway in cytochrome c oxidase. | cytochrome c oxidase is a membrane-bound enzyme that catalyzes the four-electron reduction of oxygen to water. this highly exergonic reaction drives proton pumping across the membrane. one of the key questions associated with the function of cytochrome c oxidase is how the transfer of electrons and protons is coupled and how proton transfer is controlled by the enzyme. in this study we focus on the function of one of the proton transfer pathways of the r. sphaeroides enzyme, the so-called k-prot ... | 2001 | 11296255 |
| excitation trap approach to analyze size and pigment-pigment coupling: reconstitution of lh1 antenna of rhodobacter sphaeroides with ni-substituted bacteriochlorophyll. | replacement of the central mg in chlorophylls by ni opens an ultrafast (tens of femtoseconds time range) radiationless de-excitation path, while the principal ground-state absorption and coordination properties of the pigment are retained. a method has been developed for substituting the native bacteriochlorophyll a by ni-bacteriochlorophyll a ([ni]-bchl) in the light harvesting antenna of the core complex (lh1) from the purple bacterium, rhodobacter (rb.) sphaeroides, to investigate its unit si ... | 2001 | 11297443 |
| zinc ions inhibit oxidation of cytochrome c oxidase by oxygen. | cytochrome c oxidase is a membrane-bound enzyme that catalyses the reduction of o2 to h2o and uses part of the energy released in this reaction to pump protons across the membrane. we have investigated the effect of addition of zn2+ on the kinetics of two reaction steps in cytochrome c oxidase that are associated with proton pumping; the peroxy to oxo-ferryl (p(r)-->f) and the oxo-ferryl to oxidised (f-->o) transitions. the zn2+ binding resulted in a decrease of the f-->o rate from 820 s(-1) (no ... | 2001 | 11311232 |
| regulation of nitrogenase in the photosynthetic bacterium rhodobacter sphaeroides containing dratg and nifhdk genes from rhodobacter capsulatus. | the photosynthetic bacteria rhodobacter capsulatus and rhodospirillum rubrum regulate their nitrogenase activity by the reversible adp-ribosylation of nitrogenase fe-protein in response to ammonium addition or darkness. this regulation is mediated by two enzymes, dinitrogenase reductase adp-ribosyl transferase (drat) and dinitrogenase reductase activating glycohydrolase (drag). recently, we demonstrated that another photosynthetic bacterium, rhodobacter sphaeroides, appears to have no dratg gene ... | 2001 | 11315111 |
| structure of the h subunit of the photosynthetic reaction center from the thermophilic purple sulfur bacterium, thermochromatium tepidum implications for the specific binding of the lipid molecule to the membrane protein complex. | the photosynthetic reaction center (rc) is a transmembrane protein complex that catalyzes light-driven electron transport across the photosynthetic membrane. the complete amino-acid sequence of the h subunit of the rc from a thermophilic purple sulfur bacterium, thermochromatium tepidum, has been determined for the first time among purple sulfur bacteria. the h subunit consists of 259 amino acids and has a molecular mass of 28 187. the deduced amino-acid sequences of this h subunit showed a sign ... | 2001 | 11322886 |
| ph-dependent structural changes at the heme-copper binuclear center of cytochrome c oxidase. | the resonance raman spectra of the aa3 cytochrome c oxidase from rhodobacter sphaeroides reveal ph-dependent structural changes in the binuclear site at room temperature. the binuclear site, which is the catalytic center of the enzyme, possesses two conformations at neutral ph, assessed from their distinctly different fe-co stretching modes in the resonance raman spectra of the co complex of the fully reduced enzyme. the two conformations (alpha and beta) interconvert reversibly in the ph 6-9 ra ... | 2001 | 11325707 |
| enzymatic removal of nitric oxide catalyzed by cytochrome c' in rhodobacter capsulatus. | cytochrome c' from rhodobacter capsulatus has been shown to confer resistance to nitric oxide (no). in this study, we demonstrated that the amount of cytochrome c' synthesized for buffering of no is insufficient to account for the resistance to no but that the cytochrome-dependent resistance mechanism involves the catalytic breakdown of no, under aerobic and anaerobic conditions. even under aerobic conditions, the no removal is independent of molecular oxygen, suggesting cytochrome c' is a no re ... | 2001 | 11325932 |
| the n terminus of flim is essential to promote flagellar rotation in rhodobacter sphaeroides. | flim is part of the flagellar switch complex. interaction of this protein with phospho-chey (chey-p) through its n terminus constitutes the main information relay point between the chemotactic system and the flagellum. in this work, we evaluated the role of the n terminus of flim in the swimming behavior of rhodobacter sphaeroides. strains expressing the flim protein with substitutions in residues previously reported in escherichia coli as being important for interaction with chey showed an incr ... | 2001 | 11325943 |
| c-terminal truncation and histidine-tagging of cytochrome c oxidase subunit ii reveals the native processing site, shows involvement of the c-terminus in cytochrome c binding, and improves the assay for proton pumping. | to enable metal affinity purification of cytochrome c oxidase reconstituted into phospholipid vesicles, a histidine-tag was engineered onto the c-terminal end of the rhodobacter sphaeroides cytochrome c oxidase subunit ii. characterization of the natively processed wildtype oxidase and artificially processed forms (truncated with and without a his-tag) reveals km values for cytochrome c that are 6-14-fold higher for the truncated and his-tagged forms than for the wildtype. this lowered ability t ... | 2001 | 11327819 |
| equilibrium and kinetic parameters for the binding of inhibitors to the qb pocket in bacterial chromatophores: dependence on the state of qa. | the equilibrium and kinetic parameters for the binding of various inhibitors to the q(b) pocket of the bacterial reaction center were investigated in chromatophores from rhodobacter capsulatus and rhodobacter sphaeroides. by monitoring the near-ir absorption changes specific to q(a)(-) and q(b)(-), we measured the fraction of inhibited centers in the dark and the kinetics and extent of inhibitor displacement after one flash due to the formation of the q(a)q(b)(-) state. the inhibitor release rat ... | 2001 | 11327844 |
| retardation of proton transfer caused by binding of the transition metal ion to the bacterial reaction center is due to pka shifts of key protonatable residues. | transition metal ions bind to the reaction center (rc) protein of the photosynthetic bacterium rhodobacter sphaeroides and slow the light-induced electron and proton transfer to the secondary quinone, q(b). we studied the properties of the metal ion-rc complex by measuring the ph dependence of the dissociation constant and the stoichiometry of proton release upon ligand formation. we investigated the mechanism of inhibition by measuring the stoichiometry and kinetics of flash-induced proton bind ... | 2001 | 11327848 |
| exciton delocalization probed by excitation annihilation in the light-harvesting antenna lh2. | singlet-singlet annihilation is used to study exciton delocalization in the light harvesting antenna complex lh2 (b800-b850) from the photosynthetic purple bacterium rhodobacter sphaeroides. the characteristic femtosecond decay constants of the high intensity isotropic and the low intensity anisotropy kinetics of the b850 ring are related to the hopping time tau(h) and the coherence length n(coh) of the exciton. our analysis yields n(coh) = 2.8+/-0.4 and tau(h) = 0.27+/-0.05 ps. this approach ca ... | 2001 | 11328122 |
| two enzymes of diacylglyceryl-o-4'-(n,n,n,-trimethyl)homoserine biosynthesis are encoded by btaa and btab in the purple bacterium rhodobacter sphaeroides. | betaine lipids are ether-linked, nonphosphorous glycerolipids that resemble the more commonly known phosphatidylcholine in overall structure. betaine lipids are abundant in many eukaryotes such as nonseed plants, algae, fungi, and amoeba. some of these organisms are entirely devoid of phosphatidylcholine and, instead, contain a betaine lipid such as diacylglyceryl-o-4'-(n,n,n,-trimethyl)homoserine. recently, this lipid also was discovered in the photosynthetic purple bacterium rhodobacter sphaer ... | 2001 | 11331765 |
| site specific labeling of rhodobacter sphaeroides reaction centers with dye probes for surface ph measurements. | covalently bound ph sensitive dyes are an important tool for characterizing the proteolytic reactions of protein complexes that play key roles in biological energy transduction. here we demonstrate the feasibility of this method for photosynthetic reaction centers (rcs) for the first time, by the highly selective attachment of two thiol reactive derivatives of fluorescein to the two h subunit cysteines of the photosynthetic rc from rhodobacter sphaeroides r-26 the pk(a) shifts of the dyes upon b ... | 2001 | 11334788 |
| effect of d2o and cryosolvents on the redox properties of bacteriochlorophyll dimer and electron transfer processes in rhodobacter sphaeroides reaction centers. | effects of environmental changes on the reaction pattern of excitation energy trapping and transformation into the "stable" radical pair p+q(a)-, have been analyzed in isolated reaction centers of the anoxygenic purple bacterium rhodobacter sphaeroides. the following results were obtained: (a) replacement of exchangeable protons by deuterons significantly retarded the electron transfer steps of primary charge separation, leading to the radical pair p+i- and of the subsequent reoxidation of i- by ... | 2001 | 11339312 |
| characterization of rhodobacter sphaeroides cytochrome c(2) proteins with altered heme attachment sites. | in c-type cytochromes, heme is attached to the polypeptide via thioether linkages between vinyl groups on the tetrapyrrole ring and cysteine thiols in a cx(2)ch motif. to study the role of the heme-binding site in c-type cytochrome assembly and function, we generated amino acid changes in this region of rhodobacter sphaeroides cytochrome c(2) ((15)cys-gln-thr-cys-his(19)). amino acid substitutions at cys(15), cys(18), or his(19) produced mutant proteins that did not support growth via photosynth ... | 2001 | 11339813 |
| role of the core region of the pufx protein in inhibition of reconstitution of the core light-harvesting complexes of rhodobacter sphaeroides and rhodobacter capsulatus. | pufx, the protein encoded by the pufx gene of rhodobacter capsulatus and rhodobacter sphaeroides, has been further characterized. the mature forms of these proteins contain 9 and 12 fewer amino acids, respectively, at the c-terminal end of the protein than are encoded by their pufx genes. to identify the portion of pufx responsible for inhibition of lh1 formation in reconstitution experiments, different regions (n-terminus and several core regions containing different lengths of the c-terminus) ... | 2001 | 11341824 |
| acute toxicity of (chloro-)catechols and (chloro-)catechol-copper combinations in escherichia coli corresponds to their membrane toxicity in vitro. | (chloro-)catechols are toxic for bacteria and higher organisms, but the mode of action is not yet clearly understood. we have compared the acute toxicity of different chlorinated catechols to escherichia coli with membrane toxic effects, namely narcosis and uncoupling that we have determined in an in vitro assay. in vitro membrane toxicity was quantified by measuring the accelerated decay of the membrane potential of chromatophores isolated from rhodobacter sphaeroides. both acute and membrane t ... | 2001 | 11351422 |
| cu2+ site in photosynthetic bacterial reaction centers from rhodobacter sphaeroides, rhodobacter capsulatus, and rhodopseudomonas viridis. | the interaction of metal ions with isolated photosynthetic reaction centers (rcs) from the purple bacteria rhodobacter sphaeroides, rhodobacter capsulatus, and rhodopseudomonas viridis has been investigated with transient optical and magnetic resonance techniques. in rcs from all species, the electrochromic response of the bacteriopheophytin cofactors associated with q(a)(-)q(b) --> q(a)q(b)(-) electron transfer is slowed in the presence of cu(2+). this slowing is similar to the metal ion effect ... | 2001 | 11352751 |
| a set-up to study photochemically induced dynamic nuclear polarization in photosynthetic reaction centres by solid-state nmr. | recently, solid-state nmr spectroscopy became a viable method to investigate photosynthetic reaction centres (rcs) on the atomic level. to study the electronic structure of the radical cation state of the rc, occurring after the electron emission, solid-state nmr using an illumination set-up can be exploited. this paper describes the illumination set-up we designed for a standard bruker wide-bore mas nmr probe. in addition we demonstrate its application to get information from the active site in ... | 2000 | 11355628 |
| respiratory electron transport and light-induced energy transduction in membranes from the aerobic photosynthetic bacterium roseobacter denitrificans. | membrane fragments isolated from the aerobic phototrophic bacterium roseobacter denitrificans were examined. ninety-five percent of the total nadh-dependent oxidative activity was inhibited either by antimycin a or myxothiazol, two specific inhibitors of the cytochrome bc1 complex, which indicates that the respiratory electron transport chain is linear. in agreement with this finding, light-induced oxygen uptake, an electron transport activity catalyzed by the "alternative quinol oxidase pathway ... | 2001 | 11357509 |
| probing the binding site of 800-nm bacteriochlorophyll in the membrane-linked lh2 protein of rhodobacter capsulatus by local unfolding and chemical modification: evidence for the involvement of a betahis20 residue. | the aim of this study was to investigate the function of betahis20 in the spectral behavior of the 800-nm bacteriochlorophyll (bchl) of the rhodobacter capsulatus lh2 protein. in this context, the 800-nm bchl of the membrane-linked lh2 was used as an intrinsic probe to follow the reversible, denaturant-elicited unfolding of the neighboring protein region. this band was reversibly shifted to approximately 770 nm by acidic ph, suggesting that the environment of the pigment, responsible for its nat ... | 2001 | 11358494 |
| an alternative to the accepted phylogeny of purple bacteria based on 16s rrna: analyses of the amino acid sequences of cytochromes c2 and c556 from rhodobacter (rhodovulum) sulfidophilus. | it is becoming increasingly apparent from complete genome sequences that 16s rrna data, as currently interpreted, does not provide an unambiguous picture of bacterial phylogeny. in contrast, we have found that analysis of insertions and deletions in the amino acid sequences of cytochrome c2 has some advantages in establishing relationships and that this approach may have broad utility in acquiring a better understanding of bacterial relationships. the amino acid sequences of cytochromes c2 and c ... | 2001 | 11361136 |
| investigation of the electron transfer reactions and redox characteristics of photoactive bacteriochlorophyll in rhodobacter sphaeroides reaction centers modified by d2o and cryoprotectants. | the effects of d2o, glycerol and dimethyl sulfoxide (dmso) on redox potential em of bacteriochlorophyll of a special p2 or [p(m)p(l)] pair, the rate of energy migration from bacteriopheophytin h(m) to [p(m)p(l)], electron transfer from [p(m)p(l)] to bacteriopheophytin h(l) and then to quinone q(a) in reaction centers (rc) of rhodobacter sphaeroides were studied. the h2o --> d2o substitution did not change em of the special pair, whereas addition of 70% glycerol or 35% dmso (v/v) increased the va ... | 2000 | 11368495 |
| geometric control of reduction potential in oxomolybdenum centers: implications to the serine coordination in dmso reductase. | | 2001 | 11375669 |
| main chain and side chain dynamics of a heme protein: 15n and 2h nmr relaxation studies of r. capsulatus ferrocytochrome c2. | a detailed characterization of the main chain and side chain dynamics in r. capsulatus ferrocytochrome c(2) derived from (2)h nmr relaxation of methyl group resonances is presented. (15)n relaxation measurements confirm earlier results indicating that r. capsulatus ferrocytochrome c(2) exhibits minor rotational anisotropy in solution. the current study is focused on the use of deuterium relaxation in side chain methyl groups, which has been shown to provide a detailed and accurate measure of int ... | 2001 | 11380250 |
| the gene transfer agent of rhodobacter capsulatus and "constitutive transduction" in prokaryotes. | transduction, bacteriophage-mediated gene transfer, is thought to play an important role in the evolution of prokaryote genomes. several gene transfer agents that resemble transducing phages have been found in diverse prokaryotes. this mini-review discusses these interesting agents of genetic exchange with a focus on the gene transfer agent (gta) of rhodobacter capsulatus, at present the only member of this group for which genetic information exists about the production of transducing particles. ... | 2001 | 11382219 |
| identification of the proton pathway in bacterial reaction centers: cooperation between asp-m17 and asp-l210 facilitates proton transfer to the secondary quinone (qb). | the reaction center (rc) from rhodobacter sphaeroides uses light energy to reduce and protonate a quinone molecule, q(b) (the secondary quinone electron acceptor), to form quinol, q(b)h2. asp-l210 and asp-m17 have been proposed to be components of the pathway for proton transfer [axelrod, h. l., abresch, e. c., paddock, m. l., okamura, m. y., and feher, g. (2000) proc. natl. acad. sci. u.s.a. 97, 1542-1547]. to test the importance of these residues for efficient proton transfer, the rates of the ... | 2001 | 11389604 |
| assimilation of d-malate by rhodobacter capsulatus e1f1. | rhodobacter capsulatus grew by using either l- or d-malate as carbon sources under light/anaerobic conditions. the cellular yields were the same with d- or l-malate. both l-malate dehydrogenase and l-malic enzyme activities were detected in cell-free extracts from cells grown in both isomers. by contrast, a racemase activity converting d-malate into l-malate was induced only when d-malate was present in the culture medium. this racemase activity was mn2+-dependent and was measured by coupling it ... | 2001 | 11400062 |
| characterization and sequence analysis of the replicator region of the novel plasmid palc1 from paracoccus alcaliphilus. | the replicator region of a low-copy-number plasmid, palc1, of paracoccus alcaliphilus jcm 7364 was cloned in a form of the minireplicon palc100 (3.6 kb). the host range of the minireplicon embraces several species of genus paracoccus, as well as agrobacterium tumefaciens, rhizobium leguminosarum, and rhodobacter sphaeroides (all belonging to alpha-proteobacteria), but not escherichia coli. the complete nucleotide sequence of the replicator region (2276 bp) revealed the presence of one complete o ... | 2001 | 11407917 |
| identification and characterization of a periplasmic nitrate reductase in azospirillum brasilense sp245. | the azospirillum brasilense sp245 napabc genes, encoding nitrate reductase activity, were isolated and sequenced. the derived protein sequences are very similar throughout the whole nap segment to the napabc protein sequences of escherichia coli, pseudomonas sp. g-179, ralstonia eutropha, rhodobacter sphaeroides, and paracoccus denitrificans. based on whole-cell nitrate reductase assays with the artificial electron donors benzyl viologen and methyl viologen, and assays with periplasmic cell-free ... | 2001 | 11409544 |
| taxonomic characterization of ketogulonigenium vulgare gen. nov., sp. nov. and ketogulonigenium robustum sp. nov., which oxidize l-sorbose to 2-keto-l-gulonic acid. | four bacterial strains that oxidize l-sorbose to 2-keto-l-gulonic acid, a key intermediate in the synthesis of vitamin c, were isolated from soils of geographically distinct locations. all were gram-negative, facultatively anaerobic, chemoheterotrophic rods. comparative analysis revealed nearly identical 16s rdna sequences amongst them (99.7-100% identical) and identified them as members of the alpha-subclass of the proteobacteria. phylogenetic analysis identified the closest taxonomically defin ... | 2001 | 11411674 |
| fast deuterium access to the buried magnesium/manganese site in cytochrome c oxidase. | the recently determined crystal structures of bacterial and bovine cytochrome c oxidases show an area of organized water within the protein immediately above the active site where oxygen chemistry occurs. a pathway for exit of protons or water produced during turnover is suggested by possible connections of this aqueous region to the exterior surface. a non-redox-active mg(2+) site is located in the interior of this region, and our previous studies [florens, l., hoganson, c., mccracken, j., fett ... | 2001 | 11412102 |
| electrogenic proton transfer in rhodobacter sphaeroides reaction centers: effect of coenzyme q(10) substitution by decylubiquinone in the q(b) binding site. | an electrometric technique was used to investigate the effect of coenzyme q(10) (uq), substitution by decylubiquinone (dq) at the q(b) binding site of reaction centers (uq-rc and dq-rc, respectively) on the electrogenic proton transfer kinetics upon q(b) reduction in rhodobacter sphaeroides chromatophores. unlike dq-rc, the kinetics of the second flash-induced proton uptake in uq-rc clearly deviated from the mono-exponential one. the activation energy (about 30 kj/mol) and the ph profile of the ... | 2001 | 11418124 |
| diphosphoryl lipid a from rhodobacter sphaeroides blocks the binding and internalization of lipopolysaccharide in raw 264.7 cells. | diphosphoryl lipid a derived from the nontoxic lps of rhodobacter sphaeroides (rsdpla) has been shown to be a powerful lps antagonist in both human and murine cell lines. in addition, rsdpla also can protect mice against the lethal effects of toxic lps. in this study, we complexed both the deep rough lps from escherichia coli d31 m4 (relps) and rsdpla with 5- and 30-nm colloidal gold and compared their binding to the raw 264.7 cell line by electron microscopy. both relps and rsdpla bound to the ... | 2001 | 11418686 |
| rhodobacter capsulatus nifa mutants mediating nif gene expression in the presence of ammonium. | expression of nitrogen fixation genes in rhodobacter capsulatus is repressed by ammonium at different regulatory levels including an ntrc-independent mechanism controlling nifa activity. in contrast to r. capsulatus nifa, heterologous nifa proteins of klebsiella pneumoniae and rhizobium meliloti, respectively, were not subjected to this posttranslational ammonium control in r. capsulatus. the characterization of ammonium-tolerant r. capsulatus nifa1 mutants indicated that the n-terminal domain o ... | 2001 | 11425477 |
| the orphan nuclear receptor, shp, mediates bile acid-induced inhibition of the rat bile acid transporter, ntcp. | hepatic bile acid homeostasis is regulated by negative feedback inhibition of genes involved in the uptake and synthesis of bile acids. bile acids down-regulate the rate-limiting gene for bile acid synthesis, cholesterol 7alpha-hydroxylase (cyp7a), via bile acid receptor (fxr) activation of an inhibitory nuclear receptor, shp. we hypothesized that shp would also mediate negative feedback regulation of ntcp, the principal hepatic bile acid transporter. | 2001 | 11438503 |
| the roles of the multiple chew and chea homologues in chemotaxis and in chemoreceptor localization in rhodobacter sphaeroides. | rhodobacter sphaeroides has multiple homologues of most of the escherichia coli chemotaxis genes, organized in two major operons and other, unlinked, loci. these include chea1 and chew1 (che op1) and chea2, chew2 and chew3 (che op2). we have deleted each of these chea and chew homologues in-frame and examined the chemosensory behaviour of these strains on swarm plates and in tethered cell assays. in addition, we have examined the effect of these deletions on the polar localization of the chemore ... | 2001 | 11442826 |
| roles for the rhodobacter sphaeroides ccma and ccmg proteins. | rhodobacter sphaeroides cells containing an in-frame deletion within ccma lack detectable soluble and membrane-bound c-type cytochromes and are unable to grow under conditions where these proteins are required. only strains merodiploid for ccmabcdg were found after attempting to generate cells containing either a ccmg null mutation or a ccma allele that should be polar on to expression of ccmbcdg, suggesting that ccmg has another important role in r. sphaeroides. | 2001 | 11443100 |
| mutants of chlamydomonas reinhardtii deficient in mitochondrial complex i: characterization of two mutations affecting the nd1 coding sequence. | the mitochondrial rotenone-sensitive nadh:ubiquinone oxidoreductase (complex i) comprises more than 30 subunits, the majority of which are encoded by the nucleus. in chlamydomonas reinhardtii, only five components of complex i are coded for by mitochondrial genes. three mutants deprived of complex i activity and displaying slow growth in the dark were isolated after mutagenic treatment with acriflavine. a genetical analysis demonstrated that two mutations (dum20 and dum25) affect the mitochondri ... | 2001 | 11454754 |
| interaction between cytochrome c2 and the photosynthetic reaction center from rhodobacter sphaeroides: effects of charge-modifying mutations on binding and electron transfer. | the electrostatic interactions governing binding and electron transfer from cytochrome c(2) (cyt c(2)) to the reaction center (rc) from the photosynthetic bacteria rhodobacter sphaeroides were studied by using site-directed mutagenesis to change the charges of residues on the rc surface. charge-reversing mutations (acid --> lys) decreased the binding affinity for cyt c(2). dissociation constants, k(d) (0.3--250 microm), were largest for mutations of asp m184 and nearby acid residues, identifying ... | 2001 | 11456482 |
| bis(dithiolene)molybdenum analogues relevant to the dmso reductase enzyme family: synthesis, structures, and oxygen atom transfer reactions and kinetics. | a series of dithiolene complexes of the general type [mo(iv)(qr')(s(2)c(2)me(2))(2)](1)(-) has been prepared and structurally characterized as possible structural and reactivity analogues of reduced sites of the enzymes dmsor and tmaor (qr' = pho(-), 2-ado(-), pr(i)()o(-)), dissimilatory nitrate reductase (qr' = 2-ads(-)), and formate dehydrogenase (qr' = 2-adse(-)). the complexes are square pyramidal with the molybdenum atom positioned 0.74-0.80 a above the s(4) mean plane toward axial ligand q ... | 2001 | 11456813 |
| magnetic susceptibility tensor and heme contact shifts determinations in the rhodobacter capsulatus ferricytochrome c': nmr and magnetic susceptibility studies. | the 1h and 15n resonances of the carbon monoxide complex of ferrocytochrome c' of rhodobacter capsulatus, a ferrous diamagnetic heme protein, have been extensively assigned by tocsy-hsqc, noesy-hsqc, and hsqc-noesy-hsqc 3d heteronuclear experiments performed on a 7 mm sample labeled with 15n. based on short-range and medium-range noes and h(n) exchange rates, the secondary structure consists of four helices: helix 1 (3-29), helix 2 (33-48), helix 3 (78-101), and helix 4 (103-125). the 15n, 1hn, ... | 2001 | 11456869 |
| thermal and structural changes of photosynthetic reaction centers characterized by photoacoustic detection with a broad frequency band hydrophone. | photoacoustic measurements using a broad frequency band hydrophone were carried out in photosynthetic reaction centers (rc) isolated from rhodobacter sphaeroides r-26 purple bacteria. data were extracted on enthalpy and volume changes accompanying the primary steps after excitation in the range of 0-500 microseconds aimed at further characterizing the thermodynamic properties of the rc. quinone titration showed that the volume contraction accompanying the electron transport is sensitive to the m ... | 2001 | 11460542 |
| interplay between an aaa module and an integrin i domain may regulate the function of magnesium chelatase. | in chlorophyll biosynthesis, insertion of mg(2+) into protoporphyrin ix is catalysed in an atp-dependent reaction by a three-subunit (bchi, bchd and bchh) enzyme magnesium chelatase. in this work we present the three-dimensional structure of the atp-binding subunit bchi. the structure has been solved by the multiple wavelength anomalous dispersion method and refined at 2.1 a resolution to the crystallographic r-factor of 22.2 % (r(free)=24.5 %). it belongs to the chaperone-like "atpase associate ... | 2001 | 11469861 |
| characterization of the binding of deuteroporphyrin ix to the magnesium chelatase h subunit and spectroscopic properties of the complex. | magnesium protoporphyrin chelatase catalyzes the insertion of a mg(2+) ion into protoporphyrin ix, which can be considered as the first committed step of (bacterio)chlorophyll synthesis. in the present work, the mg chelatase h subunits from both synechocystis and rhodobacter sphaeroides were studied because of the differing requirements of these organisms for modified cyclic tetrapyrroles. deuteroporphyrin was shown to be a substrate for mg chelatase. analytical hplc gel filtration was used to s ... | 2001 | 11478896 |
| mutational analysis of regulatory cis-acting elements for the transcriptional activation of the dmscba operon in rhodobacter sphaeroides f. sp. denitrificans. | four direct repeats of a 10-nt sequence, called dms boxes, are located upstream of the dmscba operon encoding dimethyl sulfoxide (dmso) reductase in rhodobacter sphaeroides f. sp. denitrificans il106. two dms boxes 1 and 2 have been shown to be binding sites of dmsr protein, a response regulator of a two-component system involved in the anaerobic induction by dmso of dmso reductase synthesis. in this study, functions of four dms boxes in the transcriptional regulation of the dmscba operon were i ... | 2001 | 11479376 |
| a novel system for heterologous expression of flavocytochrome c in phototrophic bacteria using the allochromatium vinosum rbca promoter. | flavocytochrome c-sulfide dehydrogenase (fcsd), an enzyme that catalyzes the reversible conversion of sulfide to elemental sulfur in vitro, is common to bacteria that utilize reduced sulfur compounds as electron donors in the process of carbon dioxide fixation. fcsd is a heterodimer containing two different cofactors, a flavin (fad) and one or two heme c groups, located on the separate protein subunits. efforts to produce the holoproteins of the soluble allochromatium vinosum fcsd and the membra ... | 2001 | 11479699 |
| characterisation of the mob locus of rhodobacter sphaeroides ws8: moba is the only gene required for molybdopterin guanine dinucleotide synthesis. | the mob genes of several bacteria have been implicated in the conversion of molybdopterin to molybdopterin guanine dinucleotide. the mob locus of rhodobacter sphaeroides ws8 comprises three genes, mobabc. chromosomal in-frame deletions in each of the mob genes have been constructed. the moba mutant strain has inactive dmso reductase and periplasmic nitrate reductase activities (both molybdopterin guanine dinucleotide-requiring enzymes), but the activity of xanthine dehydrogenase, a molybdopterin ... | 2001 | 11479704 |
| measuring the immeasurable. | | 2001 | 11484018 |