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dual roles of an e-helix residue, glu167, in the transcriptional activator function of cooa.cooa is a transcriptional activator that mediates co-dependent expression of the genes responsible for co oxidation in rhodospirillum rubrum. in this study, we suggest in vitro and in vivo models explaining an unusual requirement of cooa for millimolar levels of divalent cations for high-affinity dna binding. several lines of evidence indicate that an e-helix residue, glu167, plays a central role in this requirement by inhibiting sequence-specific dna binding via charge repulsion in the absence ...200515805503
electron transport to nitrogenase in rhodospirillum rubrum: identification of a new fdxn gene encoding the primary electron donor to nitrogenase.in our efforts to determine the components participating in the electron transport to nitrogenase in rhodospirillum rubrum, we have identified a gene encoding a new ferredoxin. we have generated mutants in both the new ferredoxin and ferredoxin i and demonstrate that the new ferredoxin, fdn and not the previously identified fdi is the main donor of electrons to nitrogenase.200515837392
reversible membrane association of dinitrogenase reductase activating glycohydrolase in the regulation of nitrogenase activity in rhodospirillum rubrum; dependence on glnj and amtb1.in the photosynthetic bacterium rhodospirillum rubrum nitrogenase activity is regulated by reversible adp-ribosylation of dinitrogenase reductase in response to external so called "switch-off" effectors. activation of the modified, inactive form is catalyzed by dinitrogenase reductase activating glycohydrolase (drag) which removes the adp-ribose moiety. this study addresses the signal transduction between external effectors and drag. r. rubrum, wild-type and p(ii) mutant strains, were studied wi ...200516243452
isotopic labeling of proteins by utilizing photosynthetic bacteria. 200516259936
new insights into the mechanism of nickel insertion into carbon monoxide dehydrogenase: analysis of rhodospirillum rubrum carbon monoxide dehydrogenase variants with substituted ligands to the [fe3s4] portion of the active-site c-cluster.carbon monoxide dehydrogenase (codh) from rhodospirillum rubrum catalyzes the oxidation of co to co2. a unique [nife4s4] cluster, known as the c-cluster, constitutes the active site of the enzyme. when grown in ni-deficient medium r. rubrum accumulates a ni-deficient apo form of codh that is readily activated by ni. it has been previously shown that activation of apo-codh by ni is a two-step process involving the rapid formation of an inactive apo-codh*ni complex prior to conversion to the activ ...200516283394
architecture of the native photosynthetic apparatus of phaeospirillum molischianum.the ubiquity and importance of photosynthetic organisms in nature has made the molecular mechanisms of photosynthesis a widely studied subject at both structural and functional levels. a current challenge is to understand the supramolecular assembly of the proteins involved in photosynthesis in native membranes. we have used atomic force microscopy to study the architecture of the photosynthetic apparatus and analyze the structure of single molecules in chromatophores of phaeospirillum molischia ...200516330228
titration of e. coli transhydrogenase domain iii with bound nadp+ or nadph studied by nmr reveals no ph-dependent conformational change in the physiological ph range.a ph-titration 2d nmr study of escherichia coli transhydrogenase domain iii with bound nadp(+) or nadph has been carried out, in which the ph was varied between 5.4 and 12. in this analysis, individual amide protons served as reporter groups. the apparent pk(a) values of the amide protons, determined from the ph-dependent chemical shift changes, were attributed to actual pk(a) values for several titrating residues in the protein. the essential asp392 is shown to be protonated at neutral ph in bo ...200415863102
conformational diversity in nad(h) and interacting transhydrogenase nicotinamide nucleotide binding domains.transhydrogenase (th) couples direct and stereospecific hydride transfer between nad(h) and nadp(h), bound within soluble domains i and iii, respectively, to proton translocation across membrane bound domain ii. the cocrystal structure of rhodospirillum rubrum th domains i and iii has been determined in the presence of limiting nadh, under conditions in which the subunits reach equilibrium during crystallization. the crystals contain three heterotrimeric complexes, di(2)diii, in the asymmetric u ...200415670609
carotenoid-induced cooperative formation of bacterial photosynthetic lh1 complex.a simple reconstitution technique has been developed and then applied to prepare a series of light-harvesting antenna 1 (lh1) complexes with a programmed carotenoid composition, not available from native photosynthetic membranes. the complexes were reconstituted with different c(40) carotenoids, having two structural parameters variable: the functional side groups and the number of conjugated c-c double bonds, systematically increasing from 9 to 13. the complexes, differing only in the type of c ...200415610043
investigation of the role of the n-terminal proline, the distal heme ligand in the co sensor cooa.a unique feature of cooa, a heme-containing transcription factor, is that the n-terminal proline is the distal heme ligand in the ferrous state, and this ligand is displaced upon co binding. to investigate the importance of pro(2) in co-dependent dna binding, several cooa variants that alter n-terminal ligation were characterized. electronic absorption, electron paramagnetic resonance, and magnetic circular dichroism spectra of these variants provide the most definitive evidence that pro(2) is t ...200415518565
variable lh2 stoichiometry and core clustering in native membranes of rhodospirillum photometricum.the individual components of the photosynthetic unit (psu), the light-harvesting complexes (lh2 and lh1) and the reaction center (rc), are structurally and functionally known in great detail. an important current challenge is the study of their assembly within native membranes. here, we present afm topographs at 12 a resolution of native membranes containing all constituents of the psu from rhodospirillum photometricum. besides the major technical advance represented by the acquisition of such h ...200415457213
expansion and compression of a protein folding intermediate by groel.the groel-groes chaperonin system is required for the assisted folding of many essential proteins. the precise nature of this assistance remains unclear, however. here we show that denatured rubisco from rhodospirillum rubrum populates a stable, nonaggregating, and kinetically trapped monomeric state at low temperature. productive folding of this nonnative intermediate is fully dependent on groel, groes, and atp. reactivation of the trapped rubisco monomer proceeds through a series of groel-indu ...200415469819
the "intracellular" poly(3-hydroxybutyrate) (phb) depolymerase of rhodospirillum rubrum is a periplasm-located protein with specificity for native phb and with structural similarity to extracellular phb depolymerases.rhodospirillum rubrum possesses a putative intracellular poly(3-hydroxybutyrate) (phb) depolymerase system consisting of a soluble phb depolymerase, a heat-stable activator, and a 3-hydroxybutyrate dimer hydrolase (j. m. merrick and m. doudoroff, j. bacteriol. 88:60-71, 1964). in this study we reinvestigated the soluble r. rubrum phb depolymerase (phaz1). it turned out that phaz1 is a novel type of phb depolymerase with unique properties. purified phaz1 was specific for amorphous short-chain-len ...200415489436
[an oligonucleotide primer system for amplification of the ribulose-1,5-bisphosphate carboxylase/oxygenase genes of bacteria of various taxonomic groups].based on the analysis of genbank nucleotide sequences of the cbbl and cbbm genes, coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubpc), the key enzyme of the calvin cycle, a primer system was designed that allows about 800-bp-long fragments of these genes to be pcr-ampliflied in various photo- and chemotrophic bacteria. the efficiency of the designed primer system in detection of rubpc genes was demonstrated in pcr with dna of taxonomically diverse bacteria pos ...200415315232
the reaction center h subunit is not required for high levels of light-harvesting complex 1 in rhodospirillum rubrum mutants.the gene (puha) encoding the h subunit of the reaction center (rc) was deleted by site-directed interposon mutagenesis by using a kanamycin resistance cassette lacking transcriptional terminators to eliminate polar effects in both the wild-type strain rhodospirillum rubrum s1 and the carotenoid-less strain r. rubrum g9. the puha interposon mutants were incapable of photoheterotrophic growth but grew normally under aerobic chemoheterotrophic conditions. absorption spectroscopy and sodium dodecyl ...200415317762
hypercyst mutants in rhodospirillum centenum identify regulatory loci involved in cyst cell differentiation.rhodospirillum centenum is a purple photosynthetic bacterium that forms resting cyst cells when starved for nutrients. in this study, we demonstrate that chalcone synthase gene (chsa) expression is developmentally regulated, with expression of chsa increasing up to 86-fold upon induction of the cyst developmental cycle. screening for mini-tn5-induced mutants that exhibit elevated chsa::lacz expression has led to the isolation of a set of r. centenum mutants that display increased chsa gene expre ...200415317789
active-site conformational changes associated with hydride transfer in proton-translocating transhydrogenase.transhydrogenase couples the redox (hydride-transfer) reaction between nad(h) and nadp(h) to proton translocation across a membrane. the redox reaction is catalyzed at the interface between two components (di and diii) which protrude from the membrane. a complex formed from recombinant di and diii (the di(2)diii(1) complex) from rhodospirillum rubrum transhydrogenase catalyzes fast single-turnover hydride transfer between bound nucleotides. in this report we describe three new crystal structures ...200415323555
circular dichroism of carotenoids in bacterial light-harvesting complexes: experiments and modeling.in this work we investigate the origin and characteristics of the circular dichroism (cd) spectrum of rhodopin glucoside and lycopene in the light-harvesting 2 complex of rhodopseudomonas acidophila and rhodospirillum molischianum, respectively. we successfully model their absorption and cd spectra based on the high-resolution structures. we assume that these spectra originate from seven interacting transition dipole moments: the first corresponds to the 0-0 transition of the carotenoid, whereas ...200415326029
the c-helix in cooa rolls upon co binding to ferrous heme.cooa is a homodimeric transcriptional activator from rhodospirillum rubrum containing one heme in each subunit. co binding to the heme in its sensor domain activates cooa, facilitating the binding to dna by its dna-binding domain. the c-helix links the two domains and shapes an interface between the subunits. to probe the nature of co activation, residues at positions 112-121 on the c-helix were replaced by asn or gln and their effects were evaluated by resonance raman spectroscopy and by the me ...200415326178
changing the ligand specificity of cooa, a highly specific heme-based co sensor.the co-specific heme-based sensor cooa regulates the ability of rhodospirillum rubrum to grow on co as an energy source. only co triggers the conformational change of cooa essential for the protein to function as a transcriptional activator. a structurally informed mutagenesis, followed by an in vivo screening method, allowed the isolation of a series of novel cooa variants that show very substantial response to imidazole. compared with wild-type cooa, the ligand selectivity between imidazole an ...200415326187
co-sensing mechanisms.carbon monoxide (co) has long been known to have dramatic physiological effects on organisms ranging from bacteria to humans, but recently there have a number of suggestions that organisms might have specific sensors for co. this article reviews the current evidence for a variety of proteins with demonstrated or potential co-sensing ability. particular emphasis is placed on the molecular description of cooa, a heme-containing co sensor from rhodospirillum rubrum, since its biological role as a c ...200415353565
the h(+)-pyrophosphatase of rhodospirillum rubrum is predominantly located in polyphosphate-rich acidocalcisomes.acidocalcisomes are acidic, calcium storage compartments with a h(+) pump located in their membrane that have been described in several unicellular eukaryotes, including trypanosomatid and apicomplexan parasites, algae, and slime molds, and have also been found in the bacterium agrobacterium tumefaciens. in this work, we report that the h(+)-pyrophosphatase (h(+)-ppase) of rhodospirillum rubrum, the first enzyme of this type that was identified and thought to be localized only to chromatophore m ...200415371423
similarities between the abiotic reduction of selenite with glutathione and the dissimilatory reaction mediated by rhodospirillum rubrum and escherichia coli.various mechanisms have been proposed to explain the biological dissimilatory reduction of selenite (seo3(2-)) to elemental selenium (se(o)), although none is without controversy. glutathione, the most abundant thiol in the eukaryotic cells, the cyanobacteria, and the alpha, beta, and gamma groups of the proteobacteria, has long been suspected to be involved in selenium metabolism. experiments with the phototrophic alpha proteobacterium rhodospirillum rubrum showed that the rate of selenite redu ...200415371444
importance of rhodospirillum rubrum h(+)-pyrophosphatase under low-energy conditions.the physiological role of the membrane-bound pyrophosphatase of rhodospirillum rubrum was investigated by the characterization of a mutant strain. comparisons of growth levels between the wild type and the mutant under different low-potential conditions and during transitions between different metabolisms indicate that this enzyme provides r. rubrum with an alternative energy source that is important for growth in low-energy states.200415375148
observation of calcium-dependent unidirectional rotational motion in recombinant photosynthetic f1-atpase molecules.atp hydrolysis and synthesis by the f(0)f(1)-atp synthase are coupled to proton translocation across the membrane in the presence of magnesium. calcium is known, however, to disrupt this coupling in the photosynthetic enzyme in a unique way: it does not support atp synthesis, and caatp hydrolysis is decoupled from any proton translocation, but the membrane does not become leaky to protons. understanding the molecular basis of these calcium-dependent effects can shed light on the as yet unclear m ...200415377671
functional expression and characterization of a bacterial light-harvesting membrane protein in escherichia coli and cell-free synthesis systems.heterologous expression of a bacterial light-harvesting (lh) integral membrane protein was attempted using escherichia coli cells and cell-free synthesis systems prepared from e. coli extracts. the alpha-apoprotein of lh1 complex from purple photosynthetic bacterium rhodospirillum rubrum was overexpressed as a recombinant protein with a histidine (his6) tag added to the carboxyl terminus. both of the expression systems produced alpha-apoprotein in a fully functional form as can judged by its abi ...200415388971
characterization of altered regulation variants of dinitrogenase reductase-activating glycohydrolase from rhodospirillum rubrum.in rhodospirillum rubrum, nitrogenase activity is subject to posttranslational regulation through the adenosine diphosphate (adp)-ribosylation of dinitrogenase reductase by dinitrogenase reductase adp-ribosyltransferase (drat) and dinitrogenase reductase-activating glycohydrolase (drag). to study the posttranslational regulation of drag, its gene was mutagenized and colonies screened for altered drag regulation. three different mutants were found and the drag variants displayed different biochem ...200414960312
identification of critical residues in glnb for its activation of nifa activity in the photosynthetic bacterium rhodospirillum rubrum.the p(ii) regulatory protein family is unusually widely distributed, being found in all three domains of life. three p(ii) homologs called glnb, glnk, and glnj have been identified in the photosynthetic bacterium rhodospirillum rubrum. these have roles in at least four distinct functions, one of which is activation of the nitrogen fixation-specific regulatory protein nifa. the activation of nifa requires only the covalently modified (uridylylated) form of glnb. glnk and glnj are not involved. ho ...200414970346
functionally critical elements of cooa-related co sensors.cooa is a heme-containing transcriptional activator that enables rhodospirillum rubrum to sense and grow on co as a sole energy source. we have identified a number of cooa homologs through database searches, expressed these heterologously in escherichia coli, and monitored their ability to respond to co in vivo. further in vitro analysis of two cooa homologs from azotobacter vinelandii and carboxydothermus hydrogenoformans corroborated the in vivo data by revealing the ability of co to bind to t ...200414973040
dynamics of carbon monoxide binding to cooa.cooa is a dimeric co-sensing heme protein from rhodospirillum rubrum. the heme iron in reduced cooa is six-coordinate; the axial ligands are his-77 and pro-2. co displaces pro-2 and induces a conformation change that allows cooa to bind dna and activate transcription of coo genes. equilibrium co binding is cooperative, with a hill coefficient of n = 1.4, p(50) = 2.2 microm, and estimated adair constants k(1) = 0.16 and k(2) = 1.3 microm(-1). the rates of co binding and release are both strongly ...200414990568
flexibility and size heterogeneity of the lh1 light harvesting complex revealed by atomic force microscopy: functional significance for bacterial photosynthesis.previous electron microscopic studies of bacterial rclh1 complexes demonstrated both circular and elliptical conformations of the lh1 ring, and this implied flexibility has been suggested to allow passage of quinol from the q(b) site of the rc to the quinone pool prior to reduction of the cytochrome bc(1) complex. we have used atomic force microscopy to demonstrate that these are just two of many conformations for the lh1 ring, which displays large molecule-to-molecule variations, in terms of bo ...200414993213
roles of heme axial ligands in the regulation of co binding to cooa.cooa is a co-dependent transcription factor of the bacterium rhodospirillum rubrum that contains a six-coordinate heme. it has as its heme axial ligands pro(2) and cys(75) in the ferric state and pro(2) and his(77) in the ferrous state. to probe the regulation of co binding and the ligand switching mechanism in cooa, we have prepared site-directed mutants in which the residues contributing the axial ligands are substituted. the properties of these mutants were investigated by resonance raman and ...200415026411
the fixabcx genes in rhodospirillum rubrum encode a putative membrane complex participating in electron transfer to nitrogenase.in our efforts to identify the components participating in electron transport to nitrogenase in rhodospirillum rubrum, we used mini-tn5 mutagenesis followed by metronidazole selection. one of the mutants isolated, snt-1, exhibited a decreased growth rate and about 25% of the in vivo nitrogenase activity compared to the wild-type values. the in vitro nitrogenase activity was essentially wild type, indicating that the mutation affects electron transport to nitrogenase. sequencing showed that the t ...200415028689
unraveling the function of the rhodospirillum rubrum activator of polyhydroxybutyrate (phb) degradation: the activator is a phb-granule-bound protein (phasin).efficient hydrolysis of native poly(3-hydroxybutyrate) (nphb) granules in vitro by soluble phb depolymerase of rhodospirillum rubrum requires pretreatment of nphb with an activator compound present in r. rubrum cells (j. m. merrick and m. doudoroff, j. bacteriol. 88:60-71, 1964). edman sequencing of the purified activator (17.4 kda; matrix-assisted laser desorption ionization-time of flight mass spectrometry) revealed identity to a hypothetical protein deduced from a partially sequenced r. rubru ...200415060050
low-lying excited states of light-harvesting system ii in purple bacteria.the low-lying excited states of a b850 ring of rhodospirillum (rs.) molischianum are determined accurately by a semiempirical indo/s method. results obtained are found to fit extremely well with a frenkel exciton model with long-range dipolar interactions, and the spatial size of the electron-hole pair is confirmed to fall predominantly within one bacteriochlorophyll with a small leakage to its nearest neighbors. more importantly, the nearest neighbor exciton coupling constants are found to be c ...200415089341
elucidating the role of conserved glutamates in h+-pyrophosphatase of rhodospirillum rubrum.h(+)-pyrophosphatase (h(+)-ppase) catalyzes pyrophosphate-driven proton transport against the electrochemical potential gradient in various biological membranes. all 50 of the known h(+)-ppase amino acid sequences contain four invariant glutamate residues. in this study, we use site-directed mutagenesis in conjunction with functional studies to determine the roles of the glutamate residues glu(197), glu(202), glu(550), and glu(649) in the h(+)-ppase of rhodospirillum rubrum (r-ppase). all residu ...200415107429
carbon monoxide induced decomposition of the active site [ni-4fe-5s] cluster of co dehydrogenase.during the past two years, crystal structures of cu- and mo-containing carbon monoxide dehydrogenases (codhs) and ni- and fe-containing codhs have been reported. the active site of codhs from anaerobic bacteria (cluster c) is composed of ni, fe, and s for which crystallographic studies of the enzymes from carboxydothermus hydrogenoformans, rhodospirillum rubrum, and moorella thermoaceticarevealed structural similarities in the overall protein fold but showed substantial differences in the essent ...200415113209
initial structure modification of tetrahedral to planar nickel(ii) in a nickel-iron-sulfur cluster related to the c-cluster of carbon monoxide dehydrogenase.a method has been devised that creates a planar ni(ii) site from a tetrahedral site in a nife(3)s(4) cubane-type cluster. reaction of [(ph(3)p)nife(3)s(4)(ls(3))](2)(-) (2) with 1,2-bis(dimethylphosphino)ethane affords [(dmpe)nife(3)s(4)(ls(3))](2)(-) (3), isolated in ca. 45% yield as (et(4)n)(2)[3a].2.5mecn and (et(4)n)(2)[3b].0.25mecn, both of which occur in triclinic space group p. each crystalline form contains two crystallographically inequivalent clusters with the same overall structure bu ...200415149242
a genome phylogeny for mitochondria among alpha-proteobacteria and a predominantly eubacterial ancestry of yeast nuclear genes.analyses of 55 individual and 31 concatenated protein data sets encoded in reclinomonas americana and marchantia polymorpha mitochondrial genomes revealed that current methods for constructing phylogenetic trees are insufficiently sensitive (or artifact-insensitive) to ascertain the sister of mitochondria among the current sample of eight alpha-proteobacterial genomes using mitochondrially-encoded proteins. however, rhodospirillum rubrum came as close to mitochondria as any alpha-proteobacterium ...200415155797
interactions stabilizing the structure of the core light-harvesting complex (lh1) of photosynthetic bacteria and its subunit (b820).reconstitution experiments with a chemically synthesized core light-harvesting (lh1) beta-polypeptide analogue having 3-methylhistidine instead of histidine in the position that normally donates the coordinating ligand to bacteriochlorophyll (bchl) have provided the experimental data needed to assign to b820 one of the two possible alphabeta.2bchl pairs that are observed in the crystal structure of lh2 from phaeospirillum (formerly rhodospirillum) molischianum, the one with rings iii and v of bc ...200415170338
dual flagellar systems enable motility under different circumstances.flagella are extremely effective organelles of locomotion used by a variety of bacteria and archaea. some bacteria, including aeromonas, azospirillum, rhodospirillum, and vibrio species, possess dual flagellar systems that are suited for movement under different circumstances. swimming in liquid is promoted by a single polar flagellum. swarming over surfaces or in viscous environments is enabled by the production of numerous peritrichous, or lateral, flagella. the polar flagellum is produced con ...200415170400
inhibition studies on rhodospirillum rubrum h(+)-pyrophosphatase expressed in escherichia coli.the membrane-bound proton-pumping inorganic pyrophosphatase from rhodospirillum rubrum was heterologously expressed in escherichia coli c43(de3) cells and was inhibited by 4-bromophenacyl bromide (bpb), n,n'-dicyclohexylcarbodiimid (dccd), diethyl pyrocarbonate (depc) and fluorescein 5'-isothiocyanate (fitc). in each case, the enzyme activity was rather well protected against inhibitory action by the substrate mg(2)ppi. site-directed mutagenesis was employed in attempts to identify target residu ...200415178477
the structure and function of bacterial light-harvesting complexes.the harvesting of solar radiation by purple photosynthetic bacteria is achieved by circular, integral membrane pigment-protein complexes. there are two main types of light-harvesting complex, termed lh2 and lh1, that function to absorb light energy and to transfer that energy rapidly and efficiently to the photochemical reaction centres where it is trapped. this mini-review describes our present understanding of the structure and function of the purple bacterial light-harvesting complexes.200415204626
the nitrogen-fixing gene (nifh) of rhodopseudomonas palustris: a case of lateral gene transfer?nitrogen fixation is catalysed by some photosynthetic bacteria. this paper presents a phylogenetic comparison of a nitrogen fixation gene (nifh) with the aim of elucidating the processes underlying the evolutionary history of rhodopseudomonas palustris. in the nifh phylogeny, strains of rps. palustris were placed in close association with rhodobacter spp. and other phototrophic purple non-sulfur bacteria belonging to the alpha-proteobacteria, separated from its close relatives bradyrhizobium jap ...200415256566
effect of sodium sulfide on ni-containing carbon monoxide dehydrogenases.the structure of the active-site c-cluster in co dehydrogenase from carboxydothermus hydrogenoformans includes a mu(2)-sulfide ion bridged to the ni and unique fe, whereas the same cluster in enzymes from rhodospirillum rubrum (codh(rr)) and moorella thermoacetica (codh(mt)) lack this ion. this difference was investigated by exploring the effects of sodium sulfide on activity and spectral properties. sulfide partially inhibited the co oxidation activity of codh(rr) and generated a lag prior to s ...200415264843
watching the photosynthetic apparatus in native membranes.over the last 9 years, the structures of the various components of the bacterial photosynthetic apparatus or their homologues have been determined by x-ray crystallography to at least 4.8-a resolution. despite this wealth of structural information on the individual proteins, there remains an urgent need to examine the architecture of the photosynthetic apparatus in intact photosynthetic membranes. information on the arrangement of the different complexes in a native system will help us to unders ...200415273291
oxygen-dependent h2o2 production by rubisco.oxygen and ribulose-1,5-bisphosphate dependent, h(2)o(2) production was observed with several wild type rubisco enzymes using a sensitive assay. h(2)o(2) and d-glycero-2,3-pentodiulose-1,5-bisphosphate, a known and potent inhibitor of rubisco activity, are predicted products arising from elimination of h(2)o(2) from a peroxyketone intermediate, specific to oxygenase activity. parallel assays using varying co(2) and o(2) concentrations revealed that the partitioning to h(2)o(2) during o(2) consum ...200415280029
activation mechanisms of transcriptional regulator cooa revealed by small-angle x-ray scattering.cooa, a heme-containing transcriptional activator, binds co to the heme moiety and then undergoes a structural change that promotes the specific binding to the target dna. to elucidate the activation mechanism coupled to co binding, we investigated the co-dependent structural transition of cooa with small-angle x-ray scattering (saxs). in the absence of co, the radius of gyration rg and the second virial coefficient (a2) were 25.3(+/-0.5)a and -0.39(+/-0.25) x 10(-4)ml mol g(-2), respectively. c ...200415288777
differential regulation of soluble and membrane-bound inorganic pyrophosphatases in the photosynthetic bacterium rhodospirillum rubrum provides insights into pyrophosphate-based stress bioenergetics.soluble and membrane-bound inorganic pyrophosphatases (sppase and h(+)-ppase, respectively) of the purple nonsulfur bacterium rhodospirillum rubrum are differentially regulated by environmental growth conditions. both proteins and their transcripts were found in cells of anaerobic phototrophic batch cultures along all growth phases, although they displayed different time patterns. however, in aerobic cells that grow in the dark, which exhibited the highest growth rates, northern and western blot ...200415292143
structural analysis of the reaction center light-harvesting complex i photosynthetic core complex of rhodospirillum rubrum using atomic force microscopy.the bacterium rhodospirillum rubrum contains a simple photosynthetic system, in which the reaction center (rc) receives energy from the light-harvesting (lh1) complex. we have used high-resolution atomic force microscopy (afm) to image two-dimensional crystals of the rc-lh1 complex of r. rubrum. the afm topographs show that the rc-lh1 complex is approximately 94 a in height, the rc-h subunit protrudes from the cytoplasmic face of the membrane by 40 a, and it sits 21 a above the highest point of ...200414578348
hydrophobic pockets at the membrane interface: an original mechanism for membrane protein interactions.the effect of partial digestion by trypsin and gluc protease on the association of the membrane polypeptides of lh1 from rhodospirillum (rsp.) rubrum was studied. trypsin and gluc protease treatments of lh1 result in the cleavage of the first three amino acids from the alpha polypeptide and of the first 18 amino acids from the beta polypeptide, respectively, without any noticeable reorganization of their secondary structure, as measured by attenuated total reflectance fourier transform ir spectr ...200414756563
the activator of the rhodospirillum rubrum phb depolymerase is a polypeptide that is extremely resistant to high temperature (121 degrees c) and other physical or chemical stresses.hydrolysis of native (amorphous) polyhydroxybutyrate (nphb) granules isolated from different sources by soluble phb depolymerase of rhodospirillum rubrum in vitro requires the presence of a heat-stable compound (activator). the activator was purified and was resistant against various physical and chemical stresses such as heat (up to 130 degrees c), ph 1-12, dryness, oxidation by h2o2, reducing and denaturing compounds (2-mercaptoethanol, 5 m guanidinium-hcl) and many solvents including phenol/c ...200414757249
characterization of cyst cell formation in the purple photosynthetic bacterium rhodospirillum centenum.rhodospirillum centenum is an anoxygenic photosynthetic bacterium that is capable of differentiating into several cell types. when grown phototrophically in liquid, cells exhibit a vibrioid shape and have a single polar flagellum. when grown on a solid surface, r. centenum will differentiate into rod-shaped swarm cells that display numerous lateral flagella. upon starvation for nutrients, r. centenum also forms desiccation-resistant cysts. in this study, it was determined that r. centenum has he ...200414766916
carbon monoxide dehydrogenase from rhodospirillum rubrum: effect of redox potential on catalysis.the ni-fe-s-containing c-cluster of carbon monoxide dehydrogenases is the active site for catalyzing the reversible oxidation of co to co(2). this cluster can be stabilized in redox states designated c(ox), c(red1), c(int), and c(red2). what had until recently been the best-supported mechanism of catalysis involves a one-electron reductive activation of c(ox) to c(red1) and a catalytic cycle in which the c(red1) state binds and oxidizes co, forming c(red2) and releasing co(2). recent experiments ...200414769031
removal of organics and nutrients from tannery effluent by advanced integrated wastewater pond systems technology.in this study, a pilot-scale experiment was carried out on a pre-settled combined tannery effluent from modjo tannery, ethiopia, to evaluate the feasibility of the advanced integrated wastewater pond systems or aiwps technology, for the treatment of tannery effluent. the pilot-scale aiwps facility was comprised of an advanced facultative pond (afp), secondary facultative pond (sfp) and maturation pond (mp) all arranged in series. three feed phases with low, moderate and overloading organic loadi ...200314510225
probing the transmembrane potential of bacterial cells by voltage-sensitive dyes.fluorescent dyes have been widely employed as optical indicators of the membrane potential difference in cells, isolated organelles and lipid vesicles that are too small to make microelectrode measurements feasible. we describe here the application of a carbocyanine dye, 3,3'-dipropylthiodicarbocyanine iodide [dis-c3-(5)], to monitor the transmembrane potential changes induced by a variation of the k+ concentration for the cells of escherichia (e.) coli and photosynthetic bacterium rhodospirillu ...200314516073
determination of the b820 subunit size of a bacterial core light-harvesting complex by small-angle neutron scattering.the b820 subunit is an integral pigment-membrane protein complex and can be obtained by both dissociation of the core light-harvesting complex (lh1) in photosynthetic bacteria and reconstitution from its component parts in the presence of n-octyl beta-d-glucopyranoside (og). intrinsic size of the b820 subunit from rhodospirillum rubrum lh1 complex was measured by small-angle neutron scattering in perdeuterated og solution and evaluated by guinier analysis. both the b820 subunits prepared by diss ...200314516207
a functional link between rubisco-like protein of bacillus and photosynthetic rubisco.the genomes of several nonphotosynthetic bacteria, such as bacillus subtilis, and some archaea include genes for proteins with sequence homology to the large subunit of ribulose bisphosphate carboxylase/oxygenase (rubisco). we found that such a rubisco-like protein (rlp) from b. subtilis catalyzed the 2,3-diketo-5-methylthiopentyl-1-phosphate enolase reaction in the methionine salvage pathway. a growth-defective mutant, in which the gene for this rlp had been disrupted, was rescued by the gene f ...200314551435
conformational change in the nadp(h) binding domain of transhydrogenase defines four states.proton-translocating transhydrogenase (th) couples direct and stereospecific hydride transfer between nad(h) and nadp(h), bound to soluble domains di and diii, respectively, to proton translocation across a membrane bound domain, dii. the reaction occurs with proton-gradient coupled conformational changes, which affect the energetics of substrate binding and interdomain interactions. the crystal structure of th diii from rhodospirillum rubrum has been determined in the presence of nadph (2.4 a) ...200314567675
microaerophilic cooperation of reductive and oxidative pathways allows maximal photosynthetic membrane biosynthesis in rhodospirillum rubrum.the purple nonsulfur bacterium rhodospirillum rubrum has been employed to study physiological adaptation to limiting oxygen tensions (microaerophilic conditions). r. rubrum produces maximal levels of photosynthetic membranes when grown with both succinate and fructose as carbon sources under microaerophilic conditions in comparison to the level (only about 20% of the maximum) seen in the absence of fructose. employing a unique partial o(2) pressure (po(2)) control strategy to reliably adjust the ...200314602616
biochemical and biophysical properties of the co-sensing transcriptional activator cooa.studies of heme-containing gas sensor proteins have revealed a novel function for heme, which acts as an active site for sensing the corresponding gas molecule of a physiological effector. heme-based o(2), no, and co sensor proteins have now been described in which these gas molecules act as a signaling factor that regulates the functional activity of the sensor proteins. cooa is a co-sensing transcriptional activator found in the photosynthetic bacterium rhodospirillum rubrum. the binding of co ...200314622029
proton translocation by transhydrogenase. 200314630339
identification and distribution of insertion sequences of paracoccus solventivorans.three novel insertion sequences (iss) (ispso1, ispso2, and ispso3) of the soil bacterium paracoccus solventivorans dsm 11592 were identified by transposition into entrapment vector pmec1. ispso1 (1,400 bp) carries one large open reading frame (orf) encoding a putative basic protein (with a dde motif conserved among transposases [tnps] of elements belonging to the is256 family) with the highest levels of similarity with the hypothetical tnps of rhodospirillum rubrum and sphingopyxis macrogoltabid ...200314660342
properties of mutated rhodospirillum rubrum h+-pyrophosphatase expressed in escherichia coli.the membrane-bound proton pumping inorganic pyrophosphate synthase/pyrophosphatase (h(+)-ppi synthase/h(+)-ppase) from the photosynthetic bacterium rhodospirillum rubrum was functionally expressed in escherichia coli c43(de3) cells. based on a new topology model of the enzyme, charged residues predicted to be located near or within the membrane were selected for site-directed mutagenesis. several of these mutations resulted in an almost complete inactivation of the enzyme. four mutated residues ...200314670604
direct observation of tiers in the energy landscape of a chromoprotein: a single-molecule study.single-molecule spectroscopic techniques were applied to individual pigments embedded in a chromoprotein. a sensitive tool to monitor structural fluctuations of the protein backbone in the local environment of the chromophore is provided by recording the changes of the spectral positions of the pigment absorptions as a function of time. the data provide information about the organization of the energy landscape of the protein in tiers that can be characterized by an average barrier height. addit ...200314671325
role of the c-terminal extrinsic region of the alpha polypeptide of the light-harvesting 2 complex of rhodobacter sphaeroides: a domain swap study.the lh1 and lh2 complexes of rhodobacter sphaeroides form ring structures of 16 and 9 protomers, respectively, comprising alpha and beta polypeptides, bacteriochlorophylls (bchl), and carotenoids. using the lh2 complex as a starting point, two chimeric lh complexes were constructed incorporating the alphac-terminal domain of either the rb. sphaeroides lh1 complex or the rhodospirillum molischianum lh2 complex. the lh1 domain swap produced a new red-shifted component that comprised approximately ...200314690421
purification and characterization of the polypeptides of core light-harvesting complexes from purple sulfur bacteria.although the polypeptides of core light-harvesting complexes (lh1) from many purple nonsulfur bacteria have been well characterized, little information is available on the polypeptides of lh1 from purple sulfur photosynthetic organisms. we present here the results of isolation and characterization of lh1 polypeptides from two purple sulfur bacteria, thermochromatium (tch.) tepidum and allochromatium (ach.) vinosum. native lh1 complexes were extracted and purified in a reaction center (rc)-associ ...200316245044
repositioning about the dimer interface of the transcription regulator cooa: a major signal transduction pathway between the effector and dna-binding domains.activation of the homodimeric transcriptional regulator cooa depends on the coupling of co binding at an effector domain heme with the allosteric repositioning of the dna-binding domain f-helix that promotes specific dna interaction. by analogy to the homologous camp receptor protein (crp), it has been proposed that effector binding elicits subunit reorientation about their coiled-coil c-helix interface, and that this effector domain reorientation stabilizes the active position of the dna-bindin ...200312507482
low-intensity pump-probe measurements on the b800 band of rhodospirillum molischianum.we have measured low-intensity, polarized one-color pump-probe traces in the b800 band of the light-harvesting complex lh2 of rhodospirillum molischianum at 77 k. the excitation/detection wavelength was tuned through the b800 band. a single-wavelength and a global target analysis of the data were performed with a model that accounts for excitation energy transfer among the b800 molecules and from b800 to b850. by including the anisotropy of the signals into the fitting procedure, both transfer p ...200312524297
identification and preliminary characterization of acsf, a putative ni-insertase used in the biosynthesis of acetyl-coa synthase from clostridium thermoaceticum.the acsabcde genes in the clostridium thermoaceticum genome are used for autotrophic acetyl-coa synthesis using the wood-ljungdahl pathway. a 2.8-kb region between acsc and acsd was cloned and sequenced. two open reading frames, orf7 (approximately 1.9 kb) and acsf (approximately 0.7 kb) were identified. orf7 appears to encode an fe-s protein, in that it contains five conserved cysteine residues, three of which are present in a motif (cggxxxcgxc) commonly used to coordinate fe-s clusters. howeve ...200312538050
crystal structure of a photoactive yellow protein from a sensor histidine kinase: conformational variability and signal transduction.photoactive yellow protein (e-pyp) is a blue light photoreceptor, implicated in a negative phototactic response in ectothiorhodospira halophila, that also serves as a model for the per-arnt-sim superfamily of signaling molecules. because no biological signaling partner for e-pyp has been identified, it has not been possible to correlate any of its photocycle intermediates with a relevant signaling state. however, the pyp domain (ppr-pyp) from the sensor histidine kinase ppr in rhodospirillum cen ...200312563032
glutamine 132 in the nad(h)-binding component of proton-translocating transhydrogenase tethers the nucleotides before hydride transfer.transhydrogenase, found in bacterial membranes and inner mitochondrial membranes of animal cells, couples the redox reaction between nad(h) and nadp(h) to proton translocation. in this work, the invariant gln132 in the nad(h)-binding component (di) of the rhodospirillum rubrum transhydrogenase was substituted with asn (to give di.q132n). mixtures of the mutant protein and the nadp(h)-binding component (diii) of the enzyme readily produced an asymmetric complex, (di.q132n)(2)diii(1). the x-ray st ...200312564924
single-molecule study of the electronic couplings in a circular array of molecules: light-harvesting-2 complex from rhodospirillum molischianum.applying single-molecule spectroscopic techniques allowed us to determine the mutual angles between the transition-dipole moments associated with optical transitions of the eight bacteriochlorophyll a molecules which form the so-called b800 ring of the light-harvesting-2 complex from rhodospirillum molischianum. the orientation of the transition-dipole moment is a sensitive probe for the strength of the local intermolecular interactions because of the well-defined arrangement of the individual m ...200312570608
isolation and molecular characterization of pmg160, a mobilizable cryptic plasmid from rhodobacter blasticus.a 3.4-kb cryptic plasmid was obtained from a new isolate of rhodobacter blasticus. this plasmid, designated pmg160, was mobilizable by the conjugative strain escherichia coli s17.1 into rhodobacter sphaeroides, rhodobacter capsulatus, and rhodopseudomonas palustris. it replicated in the latter strains but not in rhodospirillum rubrum, rhodocyclus gelatinosus, or bradyrhizobium species. plasmid pmg160 was stably maintained in r. sphaeroides for more than 100 generations in the absence of selectio ...200312570988
complete spectra of the far-red chemiluminescence of the oxygenase reaction of mn2+-activated ribulose-bisphosphate carboxylase/oxygenase establish excited mn2+ as the source.chemiluminescence emitted by mn(2+)-activated ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) while catalyzing oxygenation was analyzed to clarify the source of the emission. using dual detectors capturing radiation over a wide range of visible and infrared wavelengths, we tested for radiation from singlet o(2) decay and found it to be essentially absent (less than 0.1% of the total luminescence intensity). spectra were determined between 647 and 885 nm with a very sensitive, charge-co ...200312604603
[two-level heterogenous energy migration. modeling and application to purple bacteria].the dynamics of migration of electronic excitations and the efficiency of their trapping in two-dimensional ensembles of molecules were analyzed. molecules were characterized using the following parameters: the width of long-wavelength bands, the values of extinction and rate constant of deactivation of electronic excitations, critical distances of migration close to those of dye molecules, in particular, bacteriochlorophyll a and purple bacteria. a comparative analysis of two-dimensional models ...200312630112
cd bioaccumulation by a freshwater bacterium, rhodospirillum rubrum.cd bioaccumulation by rhodospirillum rubrum, a gram-negative freshwater bacterium, was studied in a synthetic medium. the free ion (cd2+) was the best predictor of the cd internalization fluxes. representation of the short-term uptake fluxes as a function of [cd2+] in the medium demonstrated a linear relationship, as would be expected for a rate-limiting, first-order internalization with a single transporter. nonetheless, several different accumulation profiles were observed, depending on the cd ...200312636267
rhodospirillum rubrum has a family i pyrophosphatase: purification, cloning, and sequencing.the cytoplasmic pyrophosphatase of the photosynthetic bacterium rhodospirillum rubrum was purified to electrophoretic homogeneity. the enzyme is a homohexamer of 20-kda monomers. the gene was cloned and sequenced. alignment of the deduced 179-amino-acid protein with known bacterial pyrophosphatases revealed conservation of all residues in the active site. attempts to obtain an insertion mutant of the cytoplasmic pyrophosphatase gene did not yield any cell completely devoid of cytoplasmic pyropho ...200312658333
ni and co: more surprises. 200312660715
rhodobacter sphaeroides has a family ii pyrophosphatase: comparison with other species of photosynthetic bacteria.the cytoplasmic pyrophosphatase from rhodobacter sphaeroides was purified and characterized. the enzyme is a homodimer of 64 kda. the n-terminus was sequenced and used to obtain the complete pyrophosphatase sequence from the preliminary genome sequence of rba. sphaeroides, showing extensive sequence similarity to family ii or class c pyrophosphatases. the enzyme hydrolyzes only mg-pp(i) and mn-pp(i) with a k(m) of 0.35 mm for both substrates. it is not activated by free mg (2+), in contrast to t ...200312669192
electron transport dynamics at the quinone acceptor site of bacterial photosynthetic reaction centers as probed using fast temperature changes.methods of laser-induced temperature jumps and fast freezing were used for testing the rates of thermoinduced conformational transitions of reaction center (rc) complexes in chromatophores and isolated rc preparations of various photosynthesizing purple bacteria. an electron transfer reaction from primary to secondary quinone acceptors was used as a probe of electron transport efficiency. the thermoinduced transition of the acceptor complex to the conformational state facilitating electron trans ...200312679860
pulsed high-frequency epr study on the location of carotenoid and chlorophyll cation radicals in photosystem ii.when the primary electron-donation pathway from the water-oxidation complex in photosystem ii (ps ii) is inhibited, chlorophyll (chl(z) and chl(d)), beta-carotene (car) and cytochrome b(559) are alternate electron donors that are believed to function in a photoprotection mechanism. previous studies have demonstrated that high-frequency epr spectroscopy (at 130 ghz), together with deuteration of ps ii, yields resolved car(+) and chl(+) epr signals (lakshmi et al. j. phys. chem. b 2000, 104, 10 44 ...200312708850
a reaction center-light-harvesting 1 complex (rc-lh1) from a rhodospirillum rubrum mutant with altered esterifying pigments: characterization by optical spectroscopy and cryo-electron microscopy.introduction of the bchp gene from rhodobacter sphaeroides encoding geranylgeranyl reductase into rhodospirillum rubrum alters the esterification of the bacteriochlorophylls so that phytol is used instead of geranylgeraniol. the resulting transconjugant strain of rs. rubrum grows photosynthetically, showing that phytolated bchla can substitute for the native pigment in both the reaction center (rc) and the light-harvesting 1 (lh1) complexes. this genetic manipulation perturbs the native caroteno ...200312719425
activation mechanism of the co sensor cooa. mutational and resonance raman spectroscopic studies.cooa is a co-dependent heme protein transcription factor of the bacterium rhodospirillum rubrum. co binding to its heme causes cooa to bind dna and activate expression of genes for co metabolism. to understand the nature of co activation, several cooa mutational variants have been studied by resonance raman spectroscopy, in vivo activity measurements, and dna binding assays. analysis of the fe-c and c-o stretching raman spectroscopy bands permits the conclusion that when co displaces the pro2 he ...200312796503
the influence of detergents and amphiphiles on the solubility of the light-harvesting i complex.the effect of detergents and amphiphiles on protein solubility and their use in crystallization solutions was examined for an integral membrane protein, the light-harvesting i complex from rhodospirillum centenum. measurement by a centrifugation assay of the solubility of the protein in different detergents and amphiphiles showed high protein-solubility values when either octyl glucoside or lauryldimethylamine-n-oxide was present with heptanetriol or when deoxycholate was present with spermine. ...200312876344
modelling continuous culture of rhodospirillum rubrum in photobioreactor under light limited conditions.rhodospirillum rubrum was grown continuously and photoheterotrophically under light limitation using a cylindrical photobioreactor in which the steady state biomass concentration was varied between 0.4 to 4 kg m(-3) at a constant radiant incident flux of 100 w m(-2). kinetic and stoichiometric models for the growth are proposed. the biomass productivities, acetate consumption rate and the co2 production rate can be quantitatively predicted to a high level of accuracy by the proposed model calcul ...200312882553
modeling stability of photoheterotrophic continuous cultures in photobioreactors.continuous cultures of the purple non-sulfur bacterium rhodospirillum rubrum were grown in a cylindrical photobioreactor in photoheterotrophic conditions, using acetate as carbon source. a new kinetic and stoichiometric knowledge model was developed, and its ability to simulate experimental results obtained under varying incident light fluxes and residence times is discussed. the model accurately predicts the stable, unstable, or oscillating behavior observed for the reactor productivity. in par ...200312892484
inter- and intraspecific variation in excited-state triplet energy transfer rates in reaction centers of photosynthetic bacteria.in protein-cofactor reaction center (rc) complexes of purple photosynthetic bacteria, the major role of the bound carotenoid (c) is to quench the triplet state formed on the primary electron donor (p) before its sensitization of the excited singlet state of molecular oxygen from its ground triplet state. this triplet energy is transferred from p to c via the bacteriochlorophyll monomer b(b). using time-resolved electron paramagnetic resonance (trepr), we have examined the temperature dependence ...200312945578
circular symmetry of the light-harvesting 1 complex from rhodospirillum rubrum is not perturbed by interaction with the reaction center.the effect of the interaction of the reaction center (rc) upon the geometrical arrangement of the bacteriochlorophyll a (bchla) pigments in the light-harvesting 1 complex (lh1) from rhodospirillum rubrum has been examined using single molecule spectroscopy. fluorescence excitation spectra at 1.8 k obtained from single detergent-solubilized as well as single membrane-reconstituted lh1-rc complexes showed predominantly (>70%) a single broad absorption maximum at 880-900 nm corresponding to the q(y ...200312950162
photosynthesis and growth of tobacco with a substituted bacterial rubisco mirror the properties of the introduced enzyme.complete replacement, by biolistic plastid transformation, of the hexadecameric ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) of tobacco (nicotiana tabacum) with the dimeric version from the bacterium, rhodospirillum rubrum, resulted in fully autotrophic and reproductive tobacco plants that required high co(2) concentrations to grow (whitney sm, andrews tj [2001] proc natl acad sci usa 98: 14738-14743). growth and photosynthesis of these plants was compared with that of nontransforme ...200312970494
tryptophan phosphorescence spectroscopy reveals that a domain in the nad(h)-binding component (di) of transhydrogenase from rhodospirillum rubrum has an extremely rigid and conformationally homogeneous protein core.the characteristics of tryptophan phosphorescence from the nad(h)-binding component (di) component of rhodospirillum rubrum transhydrogenase are described. this enzyme couples hydride transfer between nad(h) and nadp(h) to proton translocation across a membrane and is only active as a dimer. tryptophan phosphorescence spectroscopy is a sensitive technique for the detection of protein conformational changes and was used here to characterize di under mechanistically relevant conditions. our result ...200312972415
the role of the hydrophobic distal heme pocket of cooa in ligand sensing and response.cooa from rhodospirillum rubrum is a heme-containing transcriptional activator that becomes activated only upon binding co. the basis for this specificity has been probed in a cooa variant, termed deltap3r4 cooa, lacking two residues adjacent to the pro(2) heme ligand, which weakens that ligand. deltap3r4 cooa can bind imidazole and cn(-), as well as co, and form a 6-coordinate low spin adduct with each. however, in contrast to the case with co, imidazole and cn(-) do not stimulate the dna bindi ...200312433917
interaction of bacteriochlorophyll with the lh1 and pufx polypeptides of photosynthetic bacteria: use of chemically synthesized analogs and covalently attached fluorescent probes.the protein components of the reaction center (rc) and core light-harvesting (lh 1) complexes of photosynthetic bacteria have evolved to specifically, but non-covalently, bind bacteriochlorophyll (bchl). the contribution to binding of specific structural elements in the protein and bchl may be determined for the lh 1 complex because its subunit can be studied by reconstitution under equilibrium conditions. important to the determination and utilization of such information is the characterization ...200316228601
investigations of intermediates appearing in the reassociation of the light-harvesting 1 complex of rhodospirillum rubrum.we investigated the temperature-mediated reassociation of the b820 subunit of rs. rubrum to form a light-harvesting 1 complex (lh 1). by combining several spectroscopic techniques with global spectral data analysis fitting, we present evidence for the occurence of two spectral intermediates that appear during the reassociation process. at high temperatures, halfway the reassociation reaction, a prominent intermediate appears that has an absorption maximum around 850 nm, a fluorescence maximum ar ...200316228604
time-resolved dissociation of the light-harvesting 1 complex of rhodospirillum rubrum, studied by infrared laser temperature jump.for the first time, data are presented on the time-resolved disassembly reaction of a highly organized membrane protein complex in vitro. the photosynthetic core light-harvesting complex of the bacterial strain rhodospirillum rubrum g9 consists of 12-16 dimeric subunits that in vivo are associated with the photosynthetic reaction center in a ringlike manner. isolated in a detergent solution, its appearance either as a ringlike complex (called b873 and absorbing at 873 nm), subunit dimer (called ...200212484747
spectroscopic studies of nickel-deficient carbon monoxide dehydrogenase from rhodospirillum rubrum: nature of the iron-sulfur clusters.carbon monoxide dehydrogenase (codh) from rhodospirillum rubrum utilizes three types of fe-s clusters to catalyze the reversible oxidation of co to co(2): a novel [ni4fe5s] active site (c cluster) and two distinct [4fe4s] electron-transfer sites (b and d clusters). while recent x-ray data show the geometric arrangement of the five metal centers at the c cluster, electronic structures of the various [ni4fe5s] oxidation states remain ambiguous. these studies report magnetic circular dichroism (mcd ...200211814363
unsuspected diversity among marine aerobic anoxygenic phototrophs.aerobic, anoxygenic, phototrophic bacteria containing bacteriochlorophyll a (bchla) require oxygen for both growth and bchla synthesis. recent reports suggest that these bacteria are widely distributed in marine plankton, and that they may account for up to 5% of surface ocean photosynthetic electron transport and 11% of the total microbial community. known planktonic anoxygenic phototrophs belong to only a few restricted groups within the proteobacteria alpha-subclass. here we report genomic an ...200211832943
calculability analysis in underdetermined metabolic networks illustrated by a model of the central metabolism in purple nonsulfur bacteria.metabolite balancing has turned out to be a powerful computational tool in metabolic engineering. however, the linear equation systems occurring in this analysis are often underdetermined. if it is difficult or impossible to find the missing constraints, it is nevertheless feasible in some cases to determine the values of a subset of the unknown rates. here, a procedure for finding out which reaction rates can be uniquely calculated in underdetermined metabolic networks and computing these rates ...200211835134
rhodospirillum rubrum possesses a variant of the bchp gene, encoding geranylgeranyl-bacteriopheophytin reductase.the bchp gene product of rhodobacter sphaeroides is responsible for the reduction of the isoprenoid moiety of bacteriochlorophyll (bchl) from geranylgeraniol (gg) to phytol; here, we show that this enzyme also catalyzes the reduction of the isoprenoid moiety of bacteriopheophytin (bphe). in contrast, we demonstrate that a newly identified homolog of this gene in rhodospirillum rubrum encodes an enzyme, gg-bphe reductase, capable of reducing the isoprenoid moiety of bphe only. we propose that rho ...200211872709
general random matrix approach to account for the effect of static disorder on the spectral properties of light harvesting systems.we develop a random matrix model approach to study static disorder in pigment-protein complexes in photosynthetic organisms. as a case study, we examine the ring of b850 bacteriochlorophylls in the peripheral light-harvesting complex of rhodospirillum molischianum, formulated in terms of an effective hamiltonian describing the collective electronic excitations of the system. we numerically examine and compare various models of disorder and observe that both the density of states and the absorpti ...200211909118
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