| diversity of alkaliphilic halobacteria: proposals for transfer of natronobacterium vacuolatum, natronobacterium magadii, and natronobacterium pharaonis to halorubrum, natrialba, and natronomonas gen. nov., respectively, as halorubrum vacuolatum comb. nov., natrialba magadii comb. nov., and natronomonas pharaonis comb. nov., respectively. | the 16s rrna genes of three species of the genus natronobacterium (natronobacterium gregoryi, natronobacterium pharaonis, and natronobacterium vacuolatum) were sequenced and compared to that of the previously sequenced species natronobacterium magadii. the sequences revealed that natronobacterium pharaonis was phylogenetically distinct from the other members of the genus and also from other recognized genera of the family halobacteriaceae. however, natronobacterium vacuolatum and natronobacteriu ... | 1997 | 9226918 |
| diversity of extremely halophilic bacteria. | in this review, the history of the classification of the family halobacteriaceae, the extremely halophilic aerobic archaea, is reviewed with some emphasis on the recently described new genera halobaculum, halorubrum, natrialba, natronomonas, and "haloterrigena." speculation is made about the evolutionary relationship between members of the halobacteriaceae and the extremely halophilic, anaerobic methanogens of the genera methanohalobium and methanohalophilus. efforts to find missing links betwee ... | 1998 | 9783176 |
| isolation of a chymotrypsinogen b-like enzyme from the archaeon natronomonas pharaonis and other halobacteria. | a protease of a molecular mass of approximately 30kda was isolated and purified from the haloalkaliphilic archaeon natronomonas (formerly natronobacterium) pharaonis. the enzyme hydrolyzed synthetic peptides, preferentially at the carboxyl terminus of phenylalanine or leucine, as well as large proteins. hydrolysis occurred over the range of ph from 6 to 12, with an optimum at ph 10. the temperature optimum was 61 degrees c. the enzyme was nearly equally active over the range of salt concentratio ... | 1999 | 10357002 |
| radiation sensitivity of n. pharaonis in comparison with e. coli k12 strains. | to investigate the radiation sensitivity of the natronobacterium natronomonas pharaonis in comparison with escherichia coli strains (n. pharaonis dsm 2160t, e. coli strains ab1157 and k12 lambda s) were exposed to gamma-radiation (60co-gamma-source, 100 gy min-1) in the presence of oxygen (air) and under strongly reduced oxygen conditions (argon-saturated medium). after irradiation, the colony-forming ability (dose-survival curves) and the d37 dose were determined. the oxygen content of the solu ... | 2002 | 12201058 |
| diversity of archaea in hypersaline environments characterized by molecular-phylogenetic and cultivation studies. | the diversity of archaea from three different hypersaline environments was analyzed and compared by polymerase chain reaction (pcr)-based molecular phylogenetic techniques and cultivation approaches. the samples originated from a crystallization pond of a solar saltern in spain (fc); an alkaline lake in nevada, usa, (emf); and a small pond from a slag heap of a potassium mine in germany (die). except for two 16s rdna sequences that were related to crenarchaeota from soil and did not apparently b ... | 2002 | 12215811 |
| photostimulation of a sensory rhodopsin ii/htrii/tsr fusion chimera activates chea-autophosphorylation and chey-phosphotransfer in vitro. | a chimeric fusion protein consisting of natronomonas pharaonis sensory rhodopsin ii (srii), fused by a flexible linker to the two transmembrane helices of its cognate transducer protein, htrii, followed by the htrii membrane-proximal cytoplasmic fragment joined to the cytoplasmic domains of the escherichia coli chemotaxis receptor tsr, was expressed in e. coli. purified fusion chimera protein reconstituted in liposomes binds to e. coli chea kinase in the presence of the coupling protein chew, an ... | 2003 | 14636056 |
| the archaeal sensory rhodopsin ii/transducer complex: a model for transmembrane signal transfer. | archaebacterial photoreceptors mediate phototaxis by regulating cell motility through two-component signalling cascades. homologs of this sensory pathway occur in all three kingdoms of life, most notably in enteric bacteria in which the chemotaxis has been extensively studied. recent structural and functional studies on the sensory rhodopsin ii/transducer complex mediating the photophobic response of natronomonas pharaonis have yielded new insights into the mechanisms of signal transfer across t ... | 2004 | 15111099 |
| role of arg-72 of pharaonis phoborhodopsin (sensory rhodopsin ii) on its photochemistry. | pharaonis phoborhodopsin (ppr, or pharaonis sensory rhodopsin ii, npsrii) is a sensor for the negative phototaxis of natronomonas (natronobacterium) pharaonis. arginine 72 of ppr corresponds to arg-82 of bacteriorhodopsin, which is a highly conserved residue among microbial rhodopsins. using various arg-72 ppr mutants, we obtained the following results: 1). arg-72(ppr) together possibly with asp-193 influenced the pk(a) of the counterion of the protonated schiff base. 2). the m-rise became appro ... | 2004 | 15111424 |
| transient movement of helix f revealed by photo-induced inactivation by reaction of a bulky sh-reagent to cysteine-introduced pharaonis phoborhodopsin (sensory rhodopsin ii). | pharaonis phoborhodopsin (ppr) is a photosensor of negative phototaxis in natronomonas (natronobacterium) pharaonis, an alkalophilic halophile. this protein has seven transmembrane helices into which a chromophore, all-trans retinal, binds to a specific lysine residue (located in helix g)via a protonated schiff base. various mutants were engineered to have a single cysteine in the f-helix. in the presence of a bulky fluorescent sh-reagent, mians, (2-(4'-maleimidylanilino)naphthalene-6-sulfonic a ... | 2004 | 15170482 |
| light-induced intramolecular charge movements in microbial rhodopsins in intact e. coli cells. | microbial rhodopsins undergo cyclic photochemical reactions (photocycles) in which proton transfers and conformational changes result in charge displacements during transitions between photocycle intermediates. we report a new photoelectric method to monitor charge movements during rhodopsin photocycling with fast kinetic resolution in suspensions of intact e. coli cells. the method monitors electrical currents resulting from asymmetric photoexcitation of microbial rhodopsins by a unilateral las ... | 2004 | 15170484 |
| the cytoplasmic membrane-proximal domain of the htrii transducer interacts with the e-f loop of photoactivated natronomonas pharaonis sensory rhodopsin ii. | the structures of the cytoplasmic loops of the phototaxis receptor sensory rhodopsin ii (srii) and the membrane-proximal cytoplasmic domain of its bound transducer htrii were examined in the dark and in the light-activated state by fluorescent probes and cysteine cross-linking. light decreased the accessibility of e-f loop position 154 in the srii-htrii complex, but not in free srii, consistent with htrii proximity, which was confirmed by tryptophans placed within a 5-residue region identified i ... | 2004 | 15262967 |
| combined use of cultivation-dependent and cultivation-independent methods indicates that members of most haloarchaeal groups in an australian crystallizer pond are cultivable. | haloarchaea are the dominant microbial flora in hypersaline waters with near-saturating salt levels. the haloarchaeal diversity of an australian saltern crystallizer pond was examined by use of a library of pcr-amplified 16s rrna genes and by cultivation. high viable counts (10(6) cfu/ml) were obtained on solid media. long incubation times (> or =8 weeks) appeared to be more important than the medium composition for maximizing viable counts and diversity. of 66 isolates examined, all belonged to ... | 2004 | 15345408 |
| role of charged residues of pharaonis phoborhodopsin (sensory rhodopsin ii) in its interaction with the transducer protein. | pharaonis phoborhodopsin (ppr; also called pharaonis sensory rhodopsin ii, npsrii) is a receptor for negative phototaxis in natronomonas (natronobacterium) pharaonis. in membranes, it forms a 2:2 complex with its transducer protein, phtrii, which transmits light signals into the cytoplasmic space through protein-protein interactions. we previously found that a specific deprotonated carboxyl of ppr or phtrii strengthens their binding [sudo, y., et al. (2002) biophys. j. 83, 427-432]. in this stud ... | 2004 | 15504037 |
| correlation of the o-intermediate rate with the pka of asp-75 in the dark, the counterion of the schiff base of pharaonis phoborhodopsin (sensory rhodopsin ii). | pharaonis phoborhodopsin (ppr), also called pharaonis sensory rhodopsin ii, npsrii, is a photoreceptor of negative phototaxis in natronomonas (natronobacterium) pharaonis. the photocycle rate of ppr is slow compared to that of bacteriorhodopsin, despite the similarity in their x-ray structures. the decreased rate of the photocycle of ppr is a result of the longer lifetime of later photo-intermediates such as m- (ppr(m)) and o-intermediates (ppr(o)). in this study, mutants were prepared in which ... | 2005 | 15533927 |
| growth kinetics of extremely halophilic archaea (family halobacteriaceae) as revealed by arrhenius plots. | members of the family halobacteriaceae in the domain archaea are obligate extreme halophiles. they occupy a variety of hypersaline environments, and their cellular biochemistry functions in a nearly saturated salty milieu. despite extensive study, a detailed analysis of their growth kinetics is missing. to remedy this, arrhenius plots for 14 type species of the family were generated. these organisms had maximum growth temperatures ranging from 49 to 58 degrees c. nine of the organisms exhibited ... | 2005 | 15659670 |
| role of putative anion-binding sites in cytoplasmic and extracellular channels of natronomonas pharaonis halorhodopsin. | natronomonas (natronobacterium) pharaonis halorhodopsin (nphr) is an inward light-driven cl(-) ion pump. for efficient cl(-) transport, the existence of cl(-)-binding or -interacting sites in both extracellular (ec) and cytoplasmic (cp) channels is postulated. candidates include arg123 and thr126 in ec channels and lys215 and thr218 in cp channels. the roles played by these amino acid residues in anion binding and in the photocycle have been investigated by mutation of the amino acid residues at ... | 2005 | 15779904 |
| photoactivation perturbs the membrane-embedded contacts between sensory rhodopsin ii and its transducer. | the photoactivation mechanism of the sensory rho-dopsin ii (srii)-htrii receptor-transducer complex of natronomonas pharaonis was investigated by time-resolved fourier transform infrared difference spectroscopy to identify structural changes associated with early events in the signal relay mechanism from the receptor to the transducer. several prominent bands in the wild-type srii-htrii spectra are affected by amino acid substitutions at the receptor tyr(199) and transducer asn(74) residues, whi ... | 2005 | 15951432 |
| the hydroxylamine reaction of sensory rhodopsin ii: light-induced conformational alterations with c13=c14 nonisomerizable pigment. | sensory rhodopsin ii, a repellent phototaxis receptor from natronomonas (natronobacterium) pharaonis (npsrii), forms a complex with its cognate transducer (nphtrii). in micelles the two proteins form a 1:1 heterodimer, whereas in membranes they assemble to a 2:2 complex. similarly to other retinal proteins, sensory rhodopsin ii undergoes a bleaching reaction with hydroxylamine in the dark which is markedly catalyzed by light. the reaction involves cleavage of the protonated schiff base bond whic ... | 2005 | 16085771 |
| structural analysis of a hamp domain: the linker region of the phototransducer in complex with sensory rhodopsin ii. | sensory rhodopsin ii, the photophobic receptor from natronomonas pharaonis (npsrii)5, forms a 2:2 complex with its cognate transducer (n. pharaonis halobacterial transducer of rhodopsins ii (nphtrii)) in lipid membranes. light activation of npsrii leads to a displacement of helix f, which in turn triggers a rotation/screw-like motion of tm2 in nphtrii. this conformational change is thought to be transmitted through the membrane adjacent conserved signal transduction domain in histidine kinases, ... | 2005 | 16157581 |
| living with two extremes: conclusions from the genome sequence of natronomonas pharaonis. | natronomonas pharaonis is an extremely haloalkaliphilic archaeon that was isolated from salt-saturated lakes of ph 11. we sequenced its 2.6-mb gc-rich chromosome and two plasmids (131 and 23 kb). genome analysis suggests that it is adapted to cope with severe ammonia and heavy metal deficiencies that arise at high ph values. a high degree of nutritional self-sufficiency was predicted and confirmed by growth in a minimal medium containing leucine but no other amino acids or vitamins. genes for a ... | 2005 | 16169924 |
| disassembling and bleaching of chloride-free pharaonis halorhodopsin by octyl-beta-glucoside. | natronomonas (natronobacterium) pharaonis halorhodopsin (nphr) is a transmembrane, seven-helix retinal protein of the archaeal bacterium and acts as an inward light-driven chloride ion pump in the membrane. the denaturation process of nphr solubilized with n-octyl-beta-d-glucopyranoside (og) was investigated to clarify the effects of the chloride ion and ph on the stability and bleaching of the nphr chromophore. initially, active nphr solubilized with n-dodecyl-beta-d-maltopyranoside (dm) was ob ... | 2005 | 16185061 |
| effect of anions on the photocycle of halorhodopsin. substitution of chloride with formate anion. | halorhodopsin from natronomonas pharaonis is a light-driven chloride pump which transports a chloride anion across the plasma membrane following light absorption by a retinal chromophore which initiates a photocycle. it was shown that the chloride anion bound in the vicinity of retinal psb can be replaced by several inorganic anions, including azide which converts the chloride pump into a proton pump and induces formation of an m-like intermediate detected in the br photocycle but not in native ... | 2005 | 16245939 |
| [archaeal diversity of zabuye lake in tibet analyzed by culture-independent approach]. | with culture-independent approach, microbial dna was directly extracted from samples of zabuye saline soda lake. using the microbial dna as template, archaeal 16s rdnas were amplified by pcr. amplified products were cloned and sequenced. 60 different cloned partial sequences, most of which were related to haloalkaliphilic archaeon, were acquired. in the phylogenetic tree, some clones of zabuye lake belonged to genus natronobacterium, natrinema, natronococcus, natronorubrum, natronomonas, halorub ... | 2003 | 16276911 |
| effects of solubilization on the structure and function of the sensory rhodopsin ii/transducer complex. | lipid-protein interactions are known to play a crucial role in structure and physiological activity of integral membrane proteins. however, current technology for membrane protein purification necessitates extraction from the membrane into detergent micelles. also, due to experimental protocols, most of the data available for membrane proteins is obtained using detergent-solubilized samples. stable solubilization of membrane proteins is therefore an important issue in biotechnology as well as in ... | 2006 | 16410012 |
| development of the signal in sensory rhodopsin and its transfer to the cognate transducer. | the microbial phototaxis receptor sensory rhodopsin ii (npsrii, also named phoborhodopsin) mediates the photophobic response of the haloarchaeon natronomonas pharaonis by modulating the swimming behaviour of the bacterium. after excitation by blue-green light npsrii triggers, by means of a tightly bound transducer protein (nphtrii), a signal transduction chain homologous with the two-component system of eubacterial chemotaxis. two molecules of npsrii and two molecules of nphtrii form a 2:2 compl ... | 2006 | 16452929 |
| the trans-cis isomerization reaction dynamics in sensory rhodopsin ii by femtosecond time-resolved midinfrared spectroscopy: chromophore and protein dynamics. | transient infrared (ir) vibrational spectroscopy at subpicosecond time resolution on sensory rhodopsin ii from natronomonas pharaonis, npsrii, has been performed for the first time. the experiments yield three time constants for the description of the primary photoinduced reaction dynamics, i.e. 0.5, 3.7-4.4, and 11 ps. the data are consistent with a sequential reaction scheme, with the isomerization taking place within 0.5 ps, succeeded by an electronic ground state relaxation. the 11 ps compon ... | 2006 | 16475156 |
| temperature-dependent interactions between photoactivated pharaonis phoborhodopsin and its transducer. | pharaonis phoborhodopsin (ppr, also called pharaonis sensory rhodopsin ii, psrii) is a receptor for negative phototaxis in natronomonas pharaonis. in membranes, it forms a 2:2 complex with its transducer protein phtrii, and the association is weakened by 2 orders of magnitude in the m intermediate (ppr(m)). such a change is believed to correspond to the transfer of the light signal to phtrii. a previous fourier transform infrared (ftir) study observed hydrogen-bonding alteration of asn74 in phtr ... | 2006 | 16605253 |
| spin labeling of natronomonas pharaonis halorhodopsin: probing the cysteine residues environment. | halorhodopsin from natronomonas pharaonis (phr) is a light-driven chloride pump that transports a chloride anion across the plasma membrane following light absorption by a retinal chromophore which initiates a photocycle. analysis of the amino acid sequence of phr reveals three cysteine residues (cys160, cys184, and cys186) in helices d and e. here we have labeled the cysteine residues with nitroxide spin labels and studied using electron paramagnetic resonance (epr) spectroscopy their mobility, ... | 2006 | 16640441 |
| phylogenetic relationships within the order halobacteriales inferred from 16s rrna gene sequences. | phylogenetic relationships within the halophilic archaea were inferred from comparisons of the 16s rrna gene sequences from 61 strains, representing 18 genera with validly published names within the order halobacteriales. trees produced using distance-matrix (least-squares and neighbour-joining) methods affirm with strong bootstrap support that the members of the order halobacteriales are a monophyletic group. ten genera were supported as monophyletic groups [haloarcula, halobiforma, halococcus, ... | 2006 | 16738095 |
| archaeal n-terminal protein maturation commonly involves n-terminal acetylation: a large-scale proteomics survey. | we present the first large-scale survey of n-terminal protein maturation in archaea based on 873 proteomically identified n-terminal peptides from the two haloarchaea halobacterium salinarum and natronomonas pharaonis. the observed protein maturation pattern can be attributed to the combined action of methionine aminopeptidase and n-terminal acetyltransferase and applies to cytosolic proteins as well as to a large fraction of integral membrane proteins. both n-terminal maturation processes prima ... | 2006 | 16950390 |
| analysis of light-induced conformational changes of natronomonas pharaonis sensory rhodopsin ii by time resolved electron paramagnetic resonance spectroscopy. | the nature and kinetics of the conformational changes leading to the activated state of npsrii/nphtrii157 were investigated by time-resolved electron paramagnetic resonance (tr-epr) spectroscopy in combination with site-directed spin labeling (sdsl) on a series of spin labeled mutants of npsrii. a structural rearrangement of the cytoplasmic moiety of npsrii upon light activation was detected (helices b, c, f and g). the increase in distance between helices c and f in the m-trapped state of the c ... | 2007 | 16961434 |
| the distinct signaling mechanisms of microbial sensory rhodopsins in archaea, eubacteria and eukarya. | most of the known archaeal-type microbial rhodopsins are retinal-binding ion transporters, such as bacteriorhodopsin (br) and proteorhodopsin (pr). their identification is the result of extensive studies of their photochemical and biophysical properties. the cells containing these pigments, however, use other microbial rhodopsins as photosensors to monitor environmental light signals. from the early studies of sensory rhodopsin i (hssri) in halobacterium salinarum and sensory rhodopsin ii (npsri ... | 2007 | 16968113 |
| interaction of the halobacterial transducer to a halorhodopsin mutant engineered so as to bind the transducer: cl- circulation within the extracellular channel. | an alkali-halophilic archaeum, natronomonas pharaonis, contains two rhodopsins that are halorhodopsin (phr), a light-driven inward cl- pump and phoborhodopsin (ppr), the receptor of negative phototaxis functioning by forming a signaling complex with a transducer, phtrii (sudo y. et al., j. mol. biol. 357 [2006] 1274). previously, we reported that the phr double mutant, p240t/f250y(phr), can bind with phtrii. this mutant itself can transport cl-, while the net transport was stopped upon formation ... | 2007 | 16978043 |
| application of fluorescence resonance energy transfer (fret) to investigation of light-induced conformational changes of the phoborhodopsin/transducer complex. | the photoreceptor phoborhodopsin (ppr; also called sensory rhodopsin ii) forms a complex with its cognate the halobacterial transducer ii (phtrii) in the membrane, through which changes in the environmental light conditions are transmitted to the cytoplasm in natronomonas pharaonis to evoke negative phototaxis. we have applied a fluorescence resonance energy transfer (fret)-based method for investigation of the light-induced conformational changes of the ppr/phtrii complex. several far-red dyes ... | 2007 | 16978044 |
| assignment of the hydrogen-out-of-plane and -in-plane vibrations of the retinal chromophore in the k intermediate of pharaonis phoborhodopsin. | pharaonis phoborhodopsin (ppr; also called pharaonis sensory rhodopsin ii, psr-ii) is a photoreceptor protein for negative phototaxis in natronomonas pharaonis. photoisomerization of the retinal chromophore from all-trans to 13-cis initiates conformational changes of the protein leading to activation of the cognate transducer protein (phtrii). elucidation of the initial photoreaction, formation of the k intermediate of ppr, is important for understanding the mechanism of storage of photon energy ... | 2006 | 17002284 |
| tryptophan 171 in pharaonis phoborhodopsin (sensory rhodopsin ii) interacts with the chromophore retinal and its substitution with alanine or threonine slowed down the decay of m- and o-intermediate. | pharaonis phoborhodopsin (ppr), also called pharaonis sensory rhodopsin ii, npsrii, is a photoreceptor for the photophobic response of natronomonas pharaonis. tryptophan 182 (w182) of bacteriorhodopsin (br) is near the chromophore retinal and has been suggested to interact with retinal during the photoreaction and also to be involved in the hydrogen-bonding network around the retinal. w182 of br is conserved in ppr as tryptophan 171 (w171). to elucidate whether w171 of ppr interacts with retinal ... | 2007 | 17029563 |
| genome-wide proteomics of natronomonas pharaonis. | the aerobic, haloalkaliphilic archaeon natronomonas pharaonis is able to survive in salt-saturated lakes of ph 11. according to genome analysis, the theoretical proteome consists of 2843 proteins. to reach further conclusions about its cellular physiology, the cytosolic protein inventory of nmn. pharaonis has been analyzed using ms/ms on an esi-q-tof mass spectrometer coupled on-line with a nanolc system. the efficiency of this shotgun approach is illustrated by the identification of 929 protein ... | 2007 | 17203963 |
| heterologous expression of pharaonis halorhodopsin in xenopus laevis oocytes and electrophysiological characterization of its light-driven cl- pump activity. | natronomonas pharaonis halorhodopsin (phr) is an archaeal rhodopsin functioning as an inward-directed, light-driven cl- pump. to characterize the electrophysiological features of the cl- pump activity of phr, we expressed phr in xenopus laevis oocytes and analyzed its photoinduced cl- pump activity using the two-electrode voltage-clamp technique. photoinduced outward currents were observed only in the presence of cl-, br-, i-, no3-, and scn-, but not in control oocytes, indicating that photoindu ... | 2007 | 17208978 |
| expression of the halobacterial transducer protein htrii from natronomonas pharaonis in escherichia coli. | archaeal phototaxis is mediated by sensory rhodopsins which form complexes with their cognate transducers. whereas the receptors sensory rhodopsin i and sensory rhodopsin ii (srii) have been expressed in escherichia coli (e. coli) only shortened fragments of htrii from natronomonas pharaonis (nphtrii) are available. here we describe the heterologous expression of full length nphtrii which was achieved in yields of up to 0.9 mg per litre cell culture. gel filtration analysis reveals the tendency ... | 2007 | 17368449 |
| multimodal fast optical interrogation of neural circuitry. | our understanding of the cellular implementation of systems-level neural processes like action, thought and emotion has been limited by the availability of tools to interrogate specific classes of neural cells within intact, living brain tissue. here we identify and develop an archaeal light-driven chloride pump (nphr) from natronomonas pharaonis for temporally precise optical inhibition of neural activity. nphr allows either knockout of single action potentials, or sustained blockade of spiking ... | 2007 | 17410168 |
| dynamics of light-induced conformational changes of the phoborhodopsin/transducer complex formed in the n-dodecyl beta-d-maltoside micelle. | a complex of photoreceptor phoborhodopsin (ppr; also called sensory rhodopsin ii) and its cognate halobacterial transducer ii (phtrii) existing in the plasma membrane mediates the light signal to the cytoplasm in the earliest step of negative phototaxis in natronomonas pharaonis. we have investigated the dynamics of the light-induced conformational changes of the ppr/phtrii(1-159) complex formed in the presence of 0.1% n-dodecyl beta-d-maltoside (ddm) by a fluorescence resonance energy transfer ... | 2007 | 17432830 |
| large-scale identification of n-terminal peptides in the halophilic archaea halobacterium salinarum and natronomonas pharaonis. | characterization of protein n-terminal peptides supports the quality assessment of data derived from genomic sequences (e.g., the correct assignment of start codons) and hints to in vivo n-terminal modifications such as n-terminal acetylation and removal of the initiator methionine. the current work represents the first large-scale identification of n-terminal peptides from prokaryotes, of the two halophilic euryarchaeota halobacterium salinarum and natronomonas pharaonis. two methods were used ... | 2007 | 17444671 |
| constitutive activity in chimeras and deletions localize sensory rhodopsin ii/htrii signal relay to the membrane-inserted domain. | halobacterium salinarum sensory rhodopsin ii (hssrii) is a phototaxis receptor for blue-light avoidance that relays signals to its tightly bound transducer hshtrii (h. salinarum haloarchaeal transducer for srii). we found that disruption of the salt bridge between the protonated schiff base of the receptor's retinylidene chromophore and its counterion asp73 by residue substitutions d73a, n or q constitutively activates hssrii, whereas the corresponding asp75 counterion substitutions do not const ... | 2007 | 17986191 |
| structural analysis of the phototactic transducer protein htrii linker region from natronomonas pharaonis. | halobacterial pharaonis phoborhodopsin [ppr, also called natronomonas pharaonis sensory rhodopsin ii (npsrii)] is a phototaxis protein which transmits a light signal to the cytoplasm through its transducer protein (phtrii). phtrii, a two-transmembrane protein that interacts with ppr, belongs to the group of methyl-accepting chemotaxis proteins (mcps). several mutation studies have indicated that the linker region connecting the transmembrane and methylation regions is necessary for signal transd ... | 2007 | 18001143 |
| phylogenetic analysis of the archaeal community in an alkaline-saline soil of the former lake texcoco (mexico). | the soil of the former lake texcoco is an extreme environment localized in the valley of mexico city, mexico. it is highly saline and alkaline, where na+, cl(-), hco3(-) and co3(2-) are the predominant ions, with a ph ranging from 9.8 to 11.7 and electrolytic conductivities in saturation extracts from 22 to 150 ds m(-1). metagenomic dna from the archaeal community was extracted directly from soil and used as template to amplify 16s ribosomal gene by pcr. pcr products were used to construct gene ... | 2008 | 18097633 |
| characterization of alcohol dehydrogenase from the haloalkaliphilic archaeon natronomonas pharaonis. | alcohol dehydrogenase (adh; ec: 1.1.1.1) is a key enzyme in production and utilization of ethanol. in this study, the gene encoding for adh of the haloalkaliphilic archaeon natronomonas pharaonis (npadh), which has a 1,068-bp open reading frame that encodes a protein of 355 amino acids, was cloned into the pet28b vector and was expressed in escherichia coli. then, npadh was purified by ni-nta affinity chromatography. the recombinant enzyme showed a molecular mass of 41.3 kda by sds-page. the enz ... | 2008 | 18189118 |
| structural changes in the o-decay accelerated mutants of pharaonis phoborhodopsin. | pharaonis phoborhodopsin ( ppr, also called pharaonis sensory rhodopsin ii, psrii) is a receptor for negative phototaxis in natronomonas pharaonis. the x-ray crystallographic structure of ppr is very similar to those of the ion-pumping rhodopsins, bacteriorhodopsin (br) and halorhodopsin (hr). however, the decay processes of the photocycle intermediates such as m and o are much slower than those of br and hr, which is advantageous for the sensor function of ppr. iwamoto et al. previously found t ... | 2008 | 18247579 |
| metabolism of halophilic archaea. | in spite of their common hypersaline environment, halophilic archaea are surprisingly different in their nutritional demands and metabolic pathways. the metabolic diversity of halophilic archaea was investigated at the genomic level through systematic metabolic reconstruction and comparative analysis of four completely sequenced species: halobacterium salinarum, haloarcula marismortui, haloquadratum walsbyi, and the haloalkaliphile natronomonas pharaonis. the comparative study reveals different ... | 2008 | 18278431 |
| the lifetimes of pharaonis phoborhodopsin signaling states depend on the rates of proton transfers--effects of hydrostatic pressure and stopped flow experiments. | pharaonis phoborhodopsin (ppr), a negative phototaxis receptor of natronomonas pharaonis, undergoes photocycle similar to the light-driven proton pump bacteriorhodopsin (br), but the turnover rate is much slower due to much longer lifetimes of the m and o intermediates. the m decay was shown to become as fast as it is in br in the l40t/f86d mutant. we examined the effects of hydrostatic pressure on the decay of these intermediates. for br, pressure decelerated m decay but slightly affected o dec ... | 2008 | 18346087 |
| signal transfer in haloarchaeal sensory rhodopsin- transducer complexes. | membrane-inserted complexes consisting of two photochemically reactive sensory rhodopsin (sr) subunits flanking a homodimer of a transducing protein subunit (htr) are used by halophilic archaea for sensing light gradients to modulate their swimming behavior (phototaxis). the sr-htr complexes extend into the cytoplasm where the htr subunits bind a his-kinase that controls a phosphorylation system that regulates the flagellar motors. this review focuses on current progress primarily on the mechani ... | 2008 | 18346091 |
| dynamics change of phoborhodopsin and transducer by activation: study using d75n mutant of the receptor by site-directed solid-state 13c nmr. | pharaonis phoborhodopsin (ppr or sensory rhodopsin ii) is a negative phototaxis receptor of natronomonas pharaonis, and forms a complex, which transmits the photosignal into cytoplasm, with its cognate transducer (phtrii). we examined a possible local dynamics change of ppr and its d75n mutant complexed with phtrii, using solid-state (13)c nmr of [3-(13)c]ala- and [1-(13)c]val-labeled preparations. we distinguished ala c(beta) (13)c signals of relatively static stem (ala221) in the c-terminus of ... | 2008 | 18363620 |
| steric constraint in the primary photoproduct of sensory rhodopsin ii is a prerequisite for light-signal transfer to htrii. | sensory rhodopsin ii (srii, also called pharaonis phoborhodopsin, ppr) is responsible for negative phototaxis in natronomonas pharaonis. photoisomerization of the retinal chromophore from all- trans to 13- cis initiates conformational changes in the protein, leading to activation of the cognate transducer protein (htrii). we previously observed enhancement of the c 14-d stretching vibration of the retinal chromophore at 2244 cm (-1) upon formation of the k state and interpreted that a steric con ... | 2008 | 18479149 |
| lipid biomarker and phylogenetic analyses to reveal archaeal biodiversity and distribution in hypersaline microbial mat and underlying sediment. | this study has utilized the tools of lipid biomarker chemistry and molecular phylogenetic analyses to assess the archaeal contribution to diversity and abundance within a microbial mat and underlying sediment from a hypersaline lagoon in baja california. based on abundance of ether-linked isoprenoids, archaea made up from 1 to 4% of the cell numbers throughout the upper 100 mm of mat and sediment core. below this depth archaeal lipid was two times more abundant than bacterial. archaeol was the p ... | 2008 | 18564188 |
| genome information management and integrated data analysis with halolex. | halolex is a software system for the central management, integration, curation, and web-based visualization of genomic and other -omics data for any given microorganism. the system has been employed for the manual curation of three haloarchaeal genomes, namely halobacterium salinarum (strain r1), natronomonas pharaonis, and haloquadratum walsbyi. halolex, in particular, enables the integrated analysis of genome-wide proteomic results with the underlying genomic data. this has proven indispensabl ... | 2008 | 18592220 |
| a halorhodopsin-overproducing mutant isolated from an extremely haloalkaliphilic archaeon natronomonas pharaonis. | the halorhodopsin (hr)-overproducing mutant strain km-1 was isolated from the extremely haloalkaliphilic archaeon natronomonas pharaonis type strain dsm2160(t). hr-enriched membranes were easily obtained by washing the cells with distilled water. the membranes were claret colored owing to two pigments: hr and bacterioruberin. the hr component in the absorption spectra changed from blue to purple upon the addition of cl(-) and had a k(m) value of 1.7 mm. overexpression of hr in strain km-1 might ... | 2008 | 18671971 |
| enphr: a natronomonas halorhodopsin enhanced for optogenetic applications. | temporally precise inhibition of distinct cell types in the intact nervous system has been enabled by the microbial halorhodopsin nphr, a fast light-activated electrogenic cl(-) pump. while neurons can be optically hyperpolarized and inhibited from firing action potentials at moderate nphr expression levels, we have encountered challenges with pushing expression to extremely high levels, including apparent intracellular accumulations. we therefore sought to molecularly engineer nphr to achieve s ... | 2008 | 18677566 |
| transducer binding establishes localized interactions to tune sensory rhodopsin ii. | in haloarchaea, sensory rhodopsin ii (srii) mediates a photophobic response to avoid photo-oxidative damage in bright light. upon light activation the receptor undergoes a conformational change that activates a tightly bound transducer molecule (htrii), which in turn by a chain of homologous reactions transmits the signal to the chemotactic eubacterial two-component system. here, using single-molecule force spectroscopy, we localize and quantify changes to the intramolecular interactions within ... | 2008 | 18682222 |
| salt-driven equilibrium between two conformations in the hamp domain from natronomonas pharaonis: the language of signal transfer? | hamp domains (conserved in histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis proteins, and phosphatases) perform their putative function as signal transducing units in diversified environments in a variety of protein families. here the conformational changes induced by environmental agents, namely salt and temperature, on the structure and function of a hamp domain of the phototransducer from natronomonas pharaonis (nphtrii) in complex with sensory rhodopsin ii (npsrii) were inve ... | 2008 | 18697747 |
| halorhodopsin from natronomonas pharaonis forms a trimer even in the presence of a detergent, dodecyl-beta-d-maltoside. | halorhodopsin (hr) is a transmembrane seven-helix retinal protein, and acts as an inward light-driven cl(-) pump. hr from natronomonas pharaonis (nphr) can be expressed in escherichia coli inner membrane in large quantities. here, we showed that nphr forms the trimer structure even in the presence of 0.1% (2 mm) to 1% (20 mm) dodecyl-beta-d-maltoside (ddm), whose concentrations are much higher than the critical micelle concentration (0.17 mm). this conclusion was drawn from the following observa ... | 2009 | 18700862 |
| aldehyde dehydrogenase of the haloalkaliphilic archaeon natronomonas pharaonis and its function in ethanol metabolism. | the genome of natronomonas pharaonis encodes genes annotated as alcohol dehydrogenase (adh; ec 1.1.1.1) and aldehyde dehydrogenase (aldh; ec 1.2.1.3), enzymes involved in alcohol metabolism. these genes (adh and aldh2) occur in a single copy on the chromosome. we have studied the role of these genes in ethanol metabolism in n. pharaonis. reverse transcription-pcr analysis showed that the aldh2 gene was inducible by ethanol, but the adh gene was transcribed both in the presence and absence of eth ... | 2008 | 18769868 |
| ultrafast pump-probe study of the primary photoreaction process in pharaonis halorhodopsin: halide ion dependence and isomerization dynamics. | halorhodopsin is a retinal protein that acts as a light-driven chloride pump in the haloarchaeal cell membrane. a chloride ion is bound near the retinal chromophore, and light-induced all- trans --> 13- cis isomerization triggers the unidirectional chloride ion pump. we investigated the primary ultrafast dynamics of natronomonas pharaonis halorhodopsin that contains cl (-), br (-), or i (-) ( phr-cl (-), phr-br (-), or phr-i (-)) using ultrafast pump-probe spectroscopy with approximately 30 fs t ... | 2008 | 18793013 |
| sensory rhodopsin ii/transducer complex formation in detergent and in lipid bilayers studied with fret. | the photophobic receptor from natronomonas pharaonis (npsrii) forms a photo-signalling complex with its cognate transducer (nphtrii). in order to elucidate the complex formation in more detail, we have studied the intermolecular binding of both constituents (npsrii and nphtrii157; truncated at residue 157) in detergent buffers, and in lipid bilayers using fret. the data for hetero-dimer formation of npsrii/nphtrii in detergent agrees well with kd values (approximately 200 nm) described in the li ... | 2009 | 19094962 |
| proton release group of pharaonis phoborhodopsin revealed by atr-ftir spectroscopy. | the proton release mechanism has been one of the recent interesting topics in the field of microbial rhodopsins since it was established that a protonated water cluster is the proton release group(prg) in bacteriorhodopsin (br). pharaonis phoborhodopsin [ppr, also called pharaonis sensory rhodopsinii (psrii)] is a photoreceptor for negative phototaxis in natronomonas pharaonis, and in the absence of transducer protein, phtrii, ppr can pump protons like br. fast, br-like proton release was observ ... | 2009 | 19178155 |
| role of arg123 in light-driven anion pump mechanisms of pharaonis halorhodopsin. | halorhodopsin (hr) acts as a light-driven chloride pump which transports a chloride ion from the extracellular (ec) to the cytoplasmic space during a photocycle reaction that includes some photointermediates initiated by illumination. to understand the chloride uptake mechanisms, we focused on a basic residue arg123 of hr from natronomonas pharaonis (nphr), which is the only basic residue located in the ec half ion channel. by the measurements of the visible absorption spectra in the dark and th ... | 2009 | 19267875 |
| reaction dynamics of halorhodopsin studied by time-resolved diffusion. | reaction dynamics of a chloride ion pump protein, halorhodopsin (hr), from natronomonas pharaonis (n. pharaonis) (nphr) was studied by the pulsed-laser-induced transient grating (tg) method. a detailed investigation of the tg signal revealed that there is a spectrally silent diffusion process besides the absorption-observable reaction dynamics. we interpreted these dynamics in terms of release, diffusion, and uptake of the cl(-) ion. from a quantitative global analysis of the signals at various ... | 2009 | 19413978 |
| optogenetic control of epileptiform activity. | the optogenetic approach to gain control over neuronal excitability both in vitro and in vivo has emerged as a fascinating scientific tool to explore neuronal networks, but it also opens possibilities for developing novel treatment strategies for neurologic conditions. we have explored whether such an optogenetic approach using the light-driven halorhodopsin chloride pump from natronomonas pharaonis (nphr), modified for mammalian cns expression to hyperpolarize central neurons, may inhibit exces ... | 2009 | 19581573 |
| natronomonas moolapensis sp. nov., non-alkaliphilic isolates recovered from a solar saltern crystallizer pond, and emended description of the genus natronomonas. | two isolates of non-alkaliphilic, extremely halophilic archaea, with very similar characteristics, were recovered from a marine solar saltern crystallizer. cells were pleomorphic, motile and gram-stain-negative and grew on a limited range of carbon sources, with pyruvate being the best substrate. optimum growth occurred at 18-20 % (w/v) nacl, ph 6.0-8.5 and 37-40 degrees c. both isolates possessed typical archaeal lipids, and their 16s rrna gene sequences were 99.8 % identical. phylogenetic tree ... | 2010 | 19667395 |
| spin labeling epr. | site-directed spin labeling in combination with electron paramagnetic resonance spectroscopy has emerged as an efficient tool to elucidate the structure and conformational dynamics of biomolecules under native-like conditions. this article summarizes the basics as well as recent progress of site-directed spin labeling. continuous wave epr spectra analyses and pulse epr techniques are reviewed with special emphasis on applications to the sensory rhodopsin-transducer complex mediating the photopho ... | 2009 | 19728138 |
| retinal-protein interactions in halorhodopsin from natronomonas pharaonis: binding and retinal thermal isomerization catalysis. | halorhodopsin from natronomonas pharaonis (nphr) is a member of the retinal protein group and serves as a light-driven chloride pump in which chloride ions are transported through the membrane following light absorption by the retinal chromophore. in this study, we examined two main issues: (1) factors controlling the binding of the retinal chromophore to the nphr opsin and (2) the ability of the nphr opsin to catalyze the thermal isomerization of retinal isomers. we have revealed that the recon ... | 2009 | 19766652 |
| halophilic archaea cultured from ancient halite, death valley, california. | halophilic archaea cultured from ancient fluid inclusions in a 90-m-long (0- to 100,000-year-old) salt core from death valley, california, demonstrate survival of bacterial cells in subsurface halite for up to 34,000 years. five enrichment cultures, representing three genera of halophilic archaea (halorubrum, natronomonas and haloterrigena), were obtained from five surface-sterilized halite crystals exclusively in one section of the core (13.0-17.8 m; 22,000-34,000 years old) containing perennia ... | 2010 | 19840101 |
| effect of chloride binding on the thermal trimer-monomer conversion of halorhodopsin in the solubilized system. | halorhodopsin from natronomonas pharaonis (nphr) acts an inward-directed, light-driven chloride pump and forms a homotrimer. to evaluate effect of trimeric assembly, that is, intermolecular interaction, on the control or modulation of light-driven chloride pumping activity of individual hrs, it is important to understand the thermal and chloride sensitivity of trimer dissociation and the structural stability of hr. in this study, the thermal dissociation of nphr trimer to monomer in a dodecyl be ... | 2009 | 19938870 |
| crystal structure of the light-driven chloride pump halorhodopsin from natronomonas pharaonis. | the light-driven chloride pump halorhodopsin from natronomonas pharaonis (phr) crystallised into the monoclinic space group c2, with a phr trimer per the asymmetric unit. diffraction data at 2.0-a resolution showed that the carotenoid bacterioruberin binds to crevices between adjacent protein subunits in the trimeric assembly. besides seven transmembrane helices (a to g) that characterise archaeal rhodopsins, the phr protomer possesses an amphipathic alpha-helix (a') at the n-terminus. this heli ... | 2010 | 19961859 |
| improved strains and plasmid vectors for conditional overexpression of his-tagged proteins in haloferax volcanii. | research into archaea will not achieve its full potential until systems are in place to carry out genetics and biochemistry in the same species. haloferax volcanii is widely regarded as the best-equipped organism for archaeal genetics, but the development of tools for the expression and purification of h. volcanii proteins has been neglected. we have developed a series of plasmid vectors and host strains for conditional overexpression of halophilic proteins in h. volcanii. the plasmids feature t ... | 2010 | 20097827 |
| flexibility of the cytoplasmic domain of the phototaxis transducer ii from natronomonas pharaonis. | chemo- and phototaxis systems in bacteria and archaea serve as models for more complex signal transduction mechanisms in higher eukaryotes. previous studies of the cytoplasmic fragment of the phototaxis transducer (phtrii-cyt) from the halophilic archaeon natronomonas pharaonis showed that it takes the shape of a monomeric or dimeric rod under low or high salt conditions, respectively. cd spectra revealed only approximately 24% helical structure, even in 4 m kcl, leaving it an open question how ... | 2008 | 20107574 |
| complex formation and light activation in membrane-embedded sensory rhodopsin ii as seen by solid-state nmr spectroscopy. | microbial rhodopsins execute diverse biological functions in the cellular membrane. a mechanistic understanding of their functional profile is, however, still limited. we used solid-state nmr (ssnmr) spectroscopy to study structure and dynamics of a 2 x 400 amino acid sensory rhodopsin/transducer (srii/htrii) complex from natronomonas pharaonis in a natural membrane environment. we found a receptor-transducer binding interface in the ground state that significantly extends beyond the available x ... | 2010 | 20223212 |
| uv photoreactions of the extremely haloalkaliphilic euryarchaeon natronomonas pharaonis. | the objective of this study was to investigate the photobiological responses of the haloalkaliphilic euryarchaeon natronomonas pharaonis to environmentally relevant polychromatic uv radiation, simulating either the present uv radiation climate (lambda>290 nm) or that of the early earth (lambda>220 nm), and to monochromatic uvc radiation (lambda=254 nm) for comparison with the literature data. uv-induced bipyrimidine dna photoproducts were determined using a sensitive and accurate hplc tandem mas ... | 2010 | 20491923 |
| halomarina oriensis gen. nov., sp. nov., a halophilic archaeon isolated from a seawater aquarium. | a novel halophilic archaeon, strain kec-11(t), was isolated from a seawater aquarium at the ocean research institute, university of tokyo, japan. the strain was aerobic, gram-negative and chemo-organotrophic, growing optimally at 37 °c, at ph 7.0-8.0 and in 2.7 m (16 %) nacl. the strain required at least 10 mm magnesium ions for growth. cells of strain kec-11(t) were non-motile and generally irregular coccoids or discoids. the dna g+c content of the isolate was 67.7 mol%. phylogenetic tree recon ... | 2011 | 20495022 |
| structure determination of the seven-helix transmembrane receptor sensory rhodopsin ii by solution nmr spectroscopy. | seven-helix membrane proteins represent a challenge for structural biology. here we report the first nmr structure determination of a detergent-solubilized seven-helix transmembrane (7tm) protein, the phototaxis receptor sensory rhodopsin ii (psrii) from natronomonas pharaonis, as a proof of principle. the overall quality of the structure ensemble is good (backbone r.m.s. deviation of 0.48 a) and agrees well with previously determined x-ray structures. furthermore, measurements in more native-li ... | 2010 | 20512150 |
| characterization of growth and metabolism of the haloalkaliphile natronomonas pharaonis. | natronomonas pharaonis is an archaeon adapted to two extreme conditions: high salt concentration and alkaline ph. it has become one of the model organisms for the study of extremophilic life. here, we present a genome-scale, manually curated metabolic reconstruction for the microorganism. the reconstruction itself represents a knowledge base of the haloalkaliphile's metabolism and, as such, would greatly assist further investigations on archaeal pathways. in addition, we experimentally determine ... | 2010 | 20543878 |
| protein-protein interaction changes in an archaeal light-signal transduction. | negative phototaxis in natronomonas pharaonis is initiated by transient interaction changes between photoreceptor and transducer. pharaonis phoborhodopsin (ppr; also called pharaonis sensory rhodopsin ii, psr-ii) and the cognate transducer protein, phtrii, form a tight 2 : 2 complex in the unphotolyzed state, and the interaction is somehow altered during the photocycle of ppr. we have studied the signal transduction mechanism in the ppr/phtrii system by means of low-temperature fourier-transform ... | 2010 | 20671933 |
| molecular impact of the membrane potential on the regulatory mechanism of proton transfer in sensory rhodopsin ii. | metabolism establishes a potential difference across the cell membrane of every living cell which drives and regulates secondary ion and solute transfer across membrane proteins. unraveling the effect of the membrane potential on the level of single molecular groups of the membrane protein was long hampered by the lack of appropriate analytical techniques. we have developed surface enhanced infrared difference absorption spectroscopy (seidas), a highly sensitive vibrational technique for surface ... | 2010 | 20681714 |
| the photocycle of channelrhodopsin-2: ultrafast reaction dynamics and subsequent reaction steps. | the photocycle of channelrhodopsin-2 is investigated in a comprehensive study by ultrafast absorption and fluorescence spectroscopy as well as flash photolysis in the visible spectral range. the ultrafast techniques reveal an excited-state decay mechanism analogous to that of the archaeal bacteriorhodopsin and sensory rhodopsin ii from natronomonas pharaonis. after a fast vibrational relaxation of the excited-state population with 150 fs its decay with mainly 400 fs is observed. hereby, both the ... | 2010 | 20730849 |
| diversity of virus-host systems in hypersaline lake retba, senegal. | summary remarkable morphological diversity of virus-like particles was observed by transmission electron microscopy in a hypersaline water sample from lake retba, senegal. the majority of particles morphologically resembled hyperthermophilic archaeal dna viruses isolated from extreme geothermal environments. some hypersaline viral morphotypes have not been previously observed in nature, and less than 1% of observed particles had a head-and-tail morphology, which is typical for bacterial dna viru ... | 2010 | 20738373 |
| role of the hamp domain region of sensory rhodopsin transducers in signal transduction. | archaea are able to sense light via the complexes of sensory rhodopsins i and ii and their corresponding chemoreceptor-like transducers htri and htrii. though generation of the signal has been studied in detail, the mechanism of its propagation to the cytoplasm remains obscured. the cytoplasmic part of the transducer consists of adaptation and kinase activity modulating regions, connected to transmembrane helices via two hamp (histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis pro ... | 2010 | 21162553 |
| an optogenetic toolbox designed for primates. | optogenetics is a technique for controlling subpopulations of neurons in the intact brain using light. this technique has the potential to enhance basic systems neuroscience research and to inform the mechanisms and treatment of brain injury and disease. before launching large-scale primate studies, the method needs to be further characterized and adapted for use in the primate brain. we assessed the safety and efficiency of two viral vector systems (lentivirus and adeno-associated virus), two h ... | 2011 | 21278729 |
| spectroscopic evidence for the formation of an n intermediate during the photocycle of sensory rhodopsin ii (phoborhodopsin) from natronobacterium pharaonis. | sensory rhodopsin ii is a seven transmembrane helical retinal protein and functions as a photoreceptor protein in negative phototaxis of halophilic archaea. sensory rhodopsin ii from natronomonas pharaonis (npsrii) is stable under various conditions and can be expressed functionally in escherichia coli cell membranes. rhodopsins from microorganisms, known as microbial rhodopsins, exhibit a photocycle, and light irradiation of these molecules leads to a high-energy intermediate, which relaxes the ... | 2011 | 21299224 |
| chimeric microbial rhodopsins containing the third cytoplasmic loop of bovine rhodopsin. | g-protein-coupled receptors transmit stimuli (light, taste, hormone, neurotransmitter, etc.) to the intracellular signaling systems, and rhodopsin (rh) is the most-studied g-protein-coupled receptor. rh possesses an 11-cis retinal as the chromophore, and 11-cis to all-trans photoisomerization leads to the protein structural changes in the cytoplasmic loops to activate g-protein. microbial rhodopsins are similar heptahelical membrane proteins that function as bacterial sensors, light-driven ion-p ... | 2011 | 21504723 |
| the signal transfer from the receptor npsrii to the transducer nphtrii is not hampered by the d75n mutation. | sensory rhodopsin ii (npsrii) is a phototaxis receptor of natronomonas pharaonis that performs its function in complex with its cognate transducer (nphtrii). upon light activation npsrii triggers by means of nphtrii a signal transduction chain homologous to the two component system in eubacterial chemotaxis. the d75n mutant of npsrii, which lacks the blue-shifted m intermediate and therefore exhibits a significantly faster photocycle compared to the wild-type, mediates normal phototaxis response ... | 2011 | 21539797 |
| structural characteristics around the β-ionone ring of the retinal chromophore in salinibacter sensory rhodopsin i. | organisms sense and respond to environmental stimuli through membrane-embedded receptors and transducers. sensory rhodopsin i (sri) and sensory rhodopsin ii (srii) are the photoreceptors for the positive and negative phototaxis in microorganisms, respectively. they form signaling complexes in the membrane with their cognate transducer proteins, htri and htrii, and these sri-htri and srii-htrii complexes transmit a light signal through their cytoplasmic sensory signaling system, inducing opposite ... | 2011 | 21545132 |
| an amino acid residue (s201) in the retinal binding pocket regulates the photoreaction pathway of phoborhodopsin. | phoborhodopsin from halobacterium salinarum (salinarum phoborhodopsin, spr also called hssr ii) is a photoreceptor for the negative phototaxis of the bacterium. a unique feature of spr is the formation of a shorter wavelength photoproduct, p480, observed at liquid nitrogen temperature beside the k intermediate. formation of similar photoproduct has not been reported in the other microbial rhodopsins. this photoproduct showed its maximum absorbance wavelength (?(max)) at 482 nm and can thermally ... | 2011 | 21774470 |
| transmembrane signal transduction in archaeal phototaxis: the sensory rhodopsin ii-transducer complex studied by electron paramagnetic resonance spectroscopy. | archaeal photoreceptors, together with their cognate transducer proteins, mediate phototaxis by regulating cell motility through two-component signal transduction pathways. this sensory pathway is closely related to the bacterial chemotactic system, which has been studied in detail during the past 40 years. structural and functional studies applying site-directed spin labelling and electron paramagnetic resonance spectroscopy on the sensory rhodopsin ii/transducer (npsrii/nphtrii) complex of nat ... | 2011 | 21684631 |
| active state of sensory rhodopsin ii: structural determinants for signal transfer and proton pumping. | the molecular mechanism of transmembrane signal transduction is still a pertinent question in cellular biology. generally, a receptor can transfer an external signal via its cytoplasmic surface, as found for g-protein-coupled receptors such as rhodopsin, or via the membrane domain, such as that in sensory rhodopsin ii (srii) in complex with its transducer, htrii. in the absence of htrii, srii functions as a proton pump. here, we report on the crystal structure of the active state of uncomplexed ... | 2011 | 21840321 |
| Photo-induced bleaching of sensory rhodopsin II (phoborhodopsin) from Halobacterium salinarum by hydroxylamine: Identification of the responsible intermediates. | Sensory rhodopsin II from Halobacterium salinarum (HsSRII) is a retinal protein in which retinal binds to a specific lysine residue through a Schiff base. Here, we investigated the photobleaching of HsSRII in the presence of hydroxylamine. For identification of intermediate(s) attacked by hydroxylamine, we employed the flash-induced bleaching method. In order to change the concentration of intermediates, such as M- and O-intermediates, experiments were performed under varying flashlight intensit ... | 2012 | 22104601 |
| crystal structures of an o-like blue form and an anion-free yellow form of pharaonis halorhodopsin. | halorhodopsin from natronomonas pharaonis (phr) was previously crystallized into a monoclinic space group c2, and the structure of the chloride-bound purple form was determined. here, we report the crystal structures of two chloride-free forms of phr, that is, an o-like blue form and an m-like yellow form. when the c2 crystal was soaked in a chloride-free alkaline solution, the protein packing was largely altered and the yellow form containing all-trans retinal was generated. upon neutralization ... | 2011 | 21871461 |