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At least 19 recordsLinked to original sources
PubMed1997

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 Natronobacterium magadii were found to be most closely related to the genera Halorubrum and Natrialba, respectively. An unidentified haloalkaliphile, strain SSL1, was also closely related to Natronobacterium magadii and Natrialba asiatica. On the basis of phylogenetic tree reconstructions, signature bases specific for individual genera, and sequences of spacer regions between 16 and 23S rRNA genes, we propose the following changes: Natronobacterium pharaonis to be transferred to Natronomonas gen. nov. as Natronomonas pharaonis gen. nov., comb. nov.; Natronobacterium vacuolatum to be transferred to the genus Halorubrum as Halorubrum vacuolatum comb. nov.; and Natronobacterium magadii to be transferred to the genus Natrialba as Natrialba magadii.

Alkalies↗
PubMed2001

Natronobacterium nitratireducens sp. nov., a aloalkaliphilic archaeon isolated from a soda lake in China.

Two novel haloalkaliphilic archaea, strains C231T and C42, were isolated from a soda lake in China. Cells of the two strains were rod-shaped and gram-negative and colonies were bright red. They required at least 2.5 M NaCl for growth, with an optimum at 3.5 M NaCl, and grew over a pH range from 8.0 to 10.5, with an optimum at pH 8.5. Hypotonic treatment with less than 1.5 M NaCl caused cell lysis. They had similar polar lipid compositions, possessing the diphytanyl (C20:C20) and phytanyl-sesterterpanyl (C20:C25) diether derivatives of phosphatidylglycerol and phosphatidylglycerophosphate methyl ester and a minor phospholipid, PL1. No glycolipids were detected. Comparison of 16S rDNA sequences and morphological features placed them in the genus Natronobacterium. Detailed phenotypic characterization and DNA-DNA hybridization studies revealed that the two strains belong to a new species in the genus Natronobacterium, for which the name Natronobacterium nitratireducens sp. nov. is proposed. The type strain is C231T (= AS 1.1980T = JCM 10879T).

China↗
PubMed2002

Characterization of a novel halophilic archaeon, Halobiforma haloterrestris gen. nov., sp. nov., and transfer of Natronobacterium nitratireducens to Halobiforma nitratireducens comb. nov.

Strain 135(T), a novel red-pigmented, aerobic, extremely halophilic member of the Archaea showing rod, coccus and slightly pleomorphic morphology, was isolated from hypersaline soil close to Aswan (Egypt). This organism is neutrophilic, motile and requires at least 2.2 M NaCl, but no MgCl2, for growth and exhibits optimal growth at 42 degrees C. Polar lipid analysis revealed the presence of sulfated triglycosyl diether and triglycosyl diether as the sole glycolipids as well as the absence of the glycerol diether analogue of phosphatidyl glycerosulfate. C20:C20 and C20:C25 core lipids are present in almost equal proportions. The G+C content of the DNA is 66.9 mol%. 16S rDNA analysis revealed that strain 135(T) was a member of the phyletic group defined by the family Halobacteriaceae, but there was a low degree of similarity to other members of this family. Highest similarity values of 96.4 and 93.8-94.3% were obtained to the 16S rDNA of Natronobacterium nitratireducens and Natronobacterium gregoryi, Natronococcus occultus and Natronococcus amylolyticus. Strain 135(T) is able to accumulate polyhydroxybutyrate as intracellular reserve material. On the basis of the data presented, strain 135(T) should be placed in a new genus, Halobiforma gen. nov. as Halobiforma haloterrestris sp. nov. The type strain is strain 135(T) (= DSM 13078(T) = JCM 11627(T)). Moreover, the transfer of Natronobacterium nitratireducens to Halobiforma nitratireducens comb. nov. is proposed.

Base Composition↗
PubMed1997

[New species of Natronobacterium].

An extreme haloalkalophilic bacterium HAM-2 with pleomorphic rods was isolated from Hamatai soda lake in Inner Mongolia Autonomous Region. Growth occurs in 12%-30% NaCl, no growth below 12%, optimum 17.5%. pH range for good growth 7.8-10.4, optimum 9.0-9.5. The strain HAM-2 is non-motile, Gram-negative, pleomorphic, cell of which were 1.0-2.0 by 2.0-5.0 microns in size in liquid medium. The major polar lipids of the organisms are phosphatidylglycerol phosphate and phosphatidyglycerol and contains an unidentified phospholipid as a minor component PL4. G + C contant of DNA is 59.5 mol%. Based on the characteristics, the strain HAM-2 could be included in the genus Natronobacterium, but since HAM-2 differs from reported four species of this genus in cell shape, polar lipids and biochemical features. The name Natronobacterium innemongoliae sp. nov. is proposed. The type strain is designated HAM-2.

Natronobacterium↗
PubMed1997

Characterization of Natronobacterium magadii phage phi Ch1, a unique archaeal phage containing DNA and RNA.

A novel archaeal bacteriophage, phi Ch1, was isolated from a haloalkalophilic archaeon Natronobacterium magadii upon spontaneous lysis. The phage-cured strain N. magadii(L13) was used to demonstrate infectivity of phage phi Ch1. The turbid-plaque morphology and the fact that N. magadii cells isolated from plaques were able to produce phage indicated that phi Ch1 is a temperate phage. The phage morphology resembles other members of Myoviridae-infecting Halobacterium species. In solution below 2M NaCl, the phage lost its morphological stability and infectivity. One- and two-dimensional SDS-PAGE of phage particles revealed at least four major and five minor proteins with molecular masses ranging from 15 to 80 kDa and acidic isoelectric points. Southern blot analysis of chromosomal DNA of a lysogenic N. magadii strain showed that phi Ch1 exists as a chromosomally integrated prophage. The phage particles contain both double-stranded, linear DNA (approx. 55 kbp) as well as several RNA species (80-700 nucleotides). Hybridization of labelled RNA fragments to total DNA from N. magadii and phi Ch1 showed that the virion-associated RNA is host encoded. Part of the phage DNA population is modified and restriction analysis revealed evidence for adenine methylation. Phage phi Ch1 is the first virus described for the genus natronobacterium, and the first phage containing DNA and RNA in mature phage particles.

Archaea↗
PubMed1994

Lipids of extremely halophilic archaeobacteria from saline environments in India: a novel glycolipid in Natronobacterium strains.

Several strains of extremely halophilic archaeobacteria, both non-alkaliphilic and alkaliphilic, including Halobacterium, Haloferax and Natronobacterium species, were isolated from salt locales in India. The major phospholipids in these strains were the C20-C20-glycerol diether analogues of phosphatidylglycerolmethylphosphate (PGP-Me), phosphatidylglycerol (PG) and phosphatidic acid (PA). In addition, the Halobacterium strains possessed the characteristic glycolipids, sulfated triglycosyl and tetraglycosyl diethers (S-TGD-1 and S-TeGD, respectively) and the unsulfated triglycosyl diether (TGD-1); and the Haloferax strains had the characteristic sulfated and unsulfated diglycosyl glycerol diethers (S-DGD-1 and DGD-1, respectively). The PGP-Me, and PG components of the haloalkaliphiles each occurred as two molecular species with C20-C20- and C20-C25-(isopranoid) glycerol diether lipid cores. In contrast to previous reports of the absence of glycolipids in natronobacteria, the Natronobacterium strains from India were found to contain small amounts of a novel glycolipid identified as glucopyranosyl-1-->6-glucopyranosyl-1-->1-glycerol diether (DGD-4). The lipid cores of DGD-4 also contained mainly unhydroxylated or hydroxylated C20-C20, C20-C25 and C25-C25 molecular species with unsaturated (isoprenoid) chains. Hydroxylated lipid cores have previously been identified only in some methanogenic archaeobacteria.

Carbohydrate Sequence↗
PubMed1998

Nucleoside diphosphate kinase from haloalkaliphilic archaeon Natronobacterium magadii: purification and characterization.

An ATP-binding protein from the haloalkaliphilic archaeon Natronobacterium magadii was purified and characterized by affinity chromatography on ATP-agarose and by fast protein liquid chromatography (FPLC) on a Mono Q column. The N-terminal 20 amino acid sequence of the kinase showed a strong sequence similarity of this protein with nucleoside diphosphate (NDP) kinases from different organisms and, accordingly, we believe that this protein is a nucleoside diphosphate kinase, an enzyme whose main function is to exchange gamma-phosphates between nucleoside triphosphates and diphosphates. Comparison of the molecular weights of the NDP kinase monomer determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) (23,000) and of the oligomer determined by sedimentation equilibrium experiments (125,000) indicated that the oligomer is a hexamer. The enzyme was autophosphorylated in the presence of [gamma-32P]ATP, and Mg2+ was required for the incorporation of phosphate. The kinase preserved the ability to transfer gamma-phosphate from ATP to GDP in the range of NaCl concentration from 90 mM to 3.5 M and in the range of pH from 5 to 12. It was found and confirmed by Western blotting that this kinase is one of the proteins that bind specifically to natronobacterial flagellins. NDP kinase from haloalkaliphiles appeared to be simple to purify and to be a suitable enzyme for studies of structure and stability compared with NDP kinases from mesophilic organisms.

Amino Acid Sequence↗
PubMed2000

Sensory rhodopsin II from the haloalkaliphilic natronobacterium pharaonis: light-activated proton transfer reactions.

In the present work the light-activated proton transfer reactions of sensory rhodopsin II from Natronobacterium pharaonis (pSRII) and those of the channel-mutants D75N-pSRII and F86D-pSRII are investigated using flash photolysis and black lipid membrane (BLM) techniques. Whereas the photocycle of the F86D-pSRII mutant is quite similar to that of the wild-type protein, the photocycle of D75N-pSRII consists of only two intermediates. The addition of external proton donors such as azide, or in the case of F86D-pSRII, imidazole, accelerates the reprotonation of the Schiff base, but not the turnover. The electrical measurements prove that pSRII and F86D-pSRII can function as outwardly directed proton pumps, whereas the mutation in the extracellular channel (D75N-pSRII) leads to an inwardly directed transient current. The almost negligible size of the photostationary current is explained by the long-lasting photocycle of about a second. Although the M decay, but not the photocycle turnover, of pSRII and F86D-pSRII is accelerated by the addition of azide, the photostationary current is considerably increased. It is discussed that in a two-photon process a late intermediate (N- and/or O-like species) is photoconverted back to the original resting state; thereby the long photocycle is cut short, giving rise to the large increase of the photostationary current. The results presented in this work indicate that the function to generate ion gradients across membranes is a general property of archaeal rhodopsins.

Archaeal Proteins↗
PubMed2001

Static and time-resolved step-scan Fourier transform infrared investigations of the photoreaction of halorhodopsin from Natronobacterium pharaonis: consequences for models of the anion translocation mechanism.

The molecular changes during the photoreaction of halorhodopsin from Natronobacterium pharaonis have been monitored by low-temperature static and by time-resolved step-scan Fourier transform infrared difference spectroscopy. In the low-temperature L spectrum anions only influence a band around 1650 cm(-1), tentatively assigned to the C=N stretch of the protonated Schiff base of L. The analysis of the time-resolved spectra allows to identify the four states: K, L(1), L(2), and O. Between L(1) and L(2), only the apoprotein undergoes alterations. The O state is characterized by an all-trans chromophore and by rather large amide I spectral changes. Because in our analysis the intermediate containing O is in equilibrium with a state indistinguishable from L(2), we are unable to identify an N-like state. At very high chloride concentrations (>5 M), we observe a branching of the photocycle from L(2) directly back to the dark state, and we provide evidence for direct back-isomerization from L(2). This branching leads to the reported reduction of transport activity at such high chloride concentrations. We interpret the L(1) to L(2) transition as an accessibility change of the anion from the extracellular to the cytosolic side, and the large amide I bands in O as an indication for opening of the cytosolic channel from the Schiff base toward the cytosolic surface and/or as indication for changes of the binding constant of the release site.

Bacteriorhodopsins↗
PubMed2001

Temperature and halide dependence of the photocycle of halorhodopsin from Natronobacterium pharaonis.

The photocycle kinetics of halorhodopsin from Natronobacterium pharaonis (pHR(575)) was analyzed at different temperatures and chloride concentrations as well as various halides. Over the whole range of modified parameters the kinetics can be adequately modeled with six apparent rate constants. Assuming a model in which the observed rates are assigned to irreversible transitions of a single relaxation chain, six kinetically distinguishable states (P(1-6)) are discernible that are formed from four chromophore states (spectral archetypes S(j): K(570), L(N)(520), O(600), pHR'(575)). Whereas P(1) coincides with K(570) (S(1)), both P(2) and P(3) have identical spectra resembling L(520) (S(2)), thus representing a true spectral silent transition between them. P(4) constitutes a fast temperature-dependent equilibrium between the chromophore states S(2) and S(3) (L(520) and O(600), respectively). The subsequent equilibrium (P(5)) of the same spectral archetypes is only moderately temperature dependent but shows sensitivity toward the type of anion and the chloride concentration. Therefore, S(2) and S(3) occurring in P(4) as well as in P(5) have to be distinguished and are assigned to L(520)<--> O(1)(600) and O(2)(600)<--> N(520) equilibrium, respectively. It is proposed that P(4) and P(5) represent the anion release and uptake steps. Based on the experimental data affinities of the halide binding sites are estimated.

Anions↗
PubMed2002

Probing the proton channel and the retinal binding site of Natronobacterium pharaonis sensory rhodopsin II.

The sensory rhodopsin II from Natronobacterium pharaonis (NpSRII) was mutated to try to create functional properties characteristic of bacteriorhodopsin (BR), the proton pump from Halobacterium salinarum. Key residues from the cytoplasmic and extracellular proton transfer channel of BR as well as from the retinal binding site were chosen. The single site mutants L40T, F86D, P183E, and T204A did not display altered function as determined by the kinetics of their photocycles. However, the photocycle of each of the subsequent multisite mutations L40T/F86D, L40T/F86D/P183E, and L40T/F86D/P183E/T204A was quite different from that of the wild-type protein. The reprotonation of the Schiff base could be accelerated approximately 300- to 400-fold, to approximately two to three times faster than the corresponding reaction in BR. The greatest effect is observed for the quadruple mutant in which Thr-204 is replaced by Ala. This result indicates that mutations affecting conformational changes of the protein might be of decisive importance for the creation of BR-like functional properties.

Alanine↗
PubMed2003

Time-resolved FTIR studies of sensory rhodopsin II (NpSRII) from Natronobacterium pharaonis: implications for proton transport and receptor activation.

The photocycle of the photophobic receptor from Natronobacterium pharaonis, NpSRII, is studied by static and time-resolved step-scan Fourier transform infrared spectroscopy. Both low-temperature static and time-resolved spectra resolve a K-like intermediate, and the corresponding spectra show little difference within the noise of the time-resolved data. As compared to intermediate K of bacteriorhodopsin, relatively large amide I bands indicate correspondingly larger distortions of the protein backbone. The time-resolved spectra identify an intermediate L-like state with surprisingly small additional molecular alterations. With the formation of intermediate M, the Schiff-base proton is transferred to the counterion Asp-75. This state is characterized by larger amide bands indicating larger distortions of the protein. We can identify a second M state that differs only in small-protein bands. Reisomerization of the chromophore to all-trans occurs with the formation of intermediate O. The accelerated decay of intermediate M caused by azide results in another red-shifted intermediate with a protonated Schiff base. The chromophore in this state, however, still has 13-cis geometry. Nevertheless, the reisomerization is still as slow as under the conditions without azide. The results are discussed with respect to mechanisms of the observed proton pumping and the possible roles of the intermediates in receptor activation.

Archaeal Proteins↗
PubMed2003

Electric-field dependent decays of two spectroscopically different M-states of photosensory rhodopsin II from Natronobacterium pharaonis.

Sensory rhodopsin II (NpSRII) from Natronobacterium pharaonis was studied by resonance Raman (RR) spectroscopic techniques. Using gated 413-nm excitation, time-resolved RR measurements of the solubilized photoreceptor were carried out to probe the photocycle intermediates that are formed in the submillisecond time range. For the first time, two M-like intermediates were identified on the basis of their C=C stretching bands at 1568 and 1583 cm(-1), corresponding to the early M(L)(400) state with a lifetime of 30 micro s and the subsequent M(1)(400) state with a lifetime of 2 ms, respectively. The unusually high C=C stretching frequency of M(1)(400) has been attributed to an unprotonated retinal Schiff base in a largely hydrophobic environment, implying that the M(L)(400) --> M(1)(400) transition is associated with protein structural changes in the vicinity of the chromophore binding pocket. Time-resolved surface enhanced resonance Raman experiments of NpSRII electrostatically bound onto a rotating Ag electrode reveal that the photoreceptor runs through the photocycle also in the immobilized state. Surface enhanced resonance Raman spectra are very similar to the RR spectra of the solubilized protein, ruling out adsorption-induced structural changes in the retinal binding pocket. The photocycle kinetics, however, is sensitively affected by the electrode potential such that at 0.0 V (versus Ag/AgCl) the decay times of M(L)(400) and M(1)(400) are drastically slowed down. Upon decreasing the potential to -0.4 V, that corresponds to a decrease of the interfacial potential drop and thus of the electric field strength at the protein binding site, the photocycle kinetics becomes similar to that of NpSRII in solution. The electric-field dependence of the protein structural changes associated with the M-state transitions, which in the present spectroscopic work is revealed on a molecular level, appears to be related to the electric-field control of bacteriorhodopsin's photocycle, which has been shown to be of functional relevance.

Archaeal Proteins↗
PubMed1999

Time-resolved absorption and photothermal measurements with recombinant sensory rhodopsin II from Natronobacterium pharaonis.

Purified wild-type sensory rhodopsin II from Natronobacterium pharaonis (pSRII-WT) and its histidine-tagged analog (pSRII-His) were studied by laser-induced optoacoustic spectroscopy (LIOAS) and flash photolysis with optical detection. The samples were either dissolved in detergent or reconstituted into polar lipids from purple membrane (PML). The quantum yield for the formation of the long-lived state M(400) was determined as Phi(M) = 0.5 +/- 0.06 for both proteins. The structural volume change accompanying the production of K(510) as determined with LIOAS was DeltaV(R,1) </= 10 ml for both proteins, assuming Phi(K) >/= Phi(M), indicating that the His tag does not influence this early step of the photocycle. The medium has no influence on DeltaV(R,1), which is the largest so far measured for a retinal protein in this time range (<10 ns). This confirms the occurrence of conformational movements in pSRII for this step, as previously suggested by Fourier transform infrared spectroscopy. On the contrary, the decay of K(510) is an expansion in the detergent-dissolved sample and a contraction in PML. Assuming an efficiency of 1.0, DeltaV(R,2) = -3 ml/mol for pSRII-WT and -4.6 ml/mol for pSRII-His were calculated in PML, indicative of a small structural difference between the two proteins. The energy content of K(510) is also affected by the tag. It is E(K) = (88 +/- 13) for pSRII-WT and (134 +/- 11) kJ/mol for pSRII-His. A slight difference in the activation parameters for K(510) decay confirms an influence of the C-terminal His on this step. At variance with DeltaV(R,1), the opposite sign of DeltaV(R,2) in detergent and PML suggests the occurrence of solvation effects on the decay of K(510), which are probably due to a different interaction of the active site with the two dissolving media.

Archaeal Proteins↗
PubMed2000

Resonance Raman spectroscopy of sensory rhodopsin II from Natronobacterium pharaonis.

Sensory rhodopsin II (pSRII), the photophobic receptor from Natronobacterium pharaonis, has been studied by time-resolved resonance Raman (RR) spectroscopy using the rotating cell technique. Upon excitation with low laser power, the RR spectra largely reflect the parent state pSRII(500) whereas an increase of the laser power leads to a substantial accumulation of long-lived intermediates contributing to the RR spectra. All RR spectra could consistently be analysed in terms of four component spectra which were assigned to the parent state pSRII(500) and the long-lived intermediates M(400), N(485) and O(535) based on the correlation between the C = C stretching frequency and the absorption maximum. The parent state and the intermediates N(485) and O(535) exhibit a protonated Schiff base. The C = N stretching frequencies and the H/D isotopic shifts indicate strong hydrogen bonding interactions of the Schiff base in pSRII(500) and O(535) whereas these interactions are most likely very weak in N(485).

Archaeal Proteins↗
PubMed1998

Heterologous coexpression of the blue light receptor psRII and its transducer pHtrII from Natronobacterium pharaonis in the Halobacterium salinarium strain Pho81/w restores negative phototaxis.

The photophobic receptor (psRII) and its transducer pHtrII from Natronobacterium pharaonis were heterologously coexpressed in the phototaxis-deficient Halobacterium salinarium strain Pho81/w which lacks all four bacterial rhodopsins, i.e. the two ion pumps bacteriorhodopsin and halorhodopsin as well as the two sensory pigments SRI and SRII. This genetically transformed Pho81/w strain showed a photophobic response upon illumination with blue light. The action spectrum of the psRII/pHtrII mediated phototactic behavior was determined in the range of 420-600 nm. The shape of the action spectrum was similar to the absorption spectrum of psRII, clearly indicating that the psRII-specific photophobic response in Pho81/w was restored. These results suggest that the pharaonis photoreceptor-transducer complex (psRII/pHtrII) is functionally competent to substitute the corresponding salinarium receptor system. Although the two archaea are phylogenetically quite distant from each other the two signal transduction chains are homologous systems which can replace each other.

Archaeal Proteins↗
PubMed2003

Ser-130 of Natronobacterium pharaonis halorhodopsin is important for the chloride binding.

Pharaonis halorhodopsin (phR) is an inward light-driven chloride ion pump from Natronobacterium pharaonis. In order to clarify the role of Ser-130(phR) residue which corresponds to Ser-115(shR) for salinarum hR on the anion-binding affinity, the wild-type and Ser-130 mutants substituted with Thr, Cys and Ala were expressed in E. coli cells and solubilized with 0.1% n-dodecyl beta-D-maltopyranoside The absorption maximum (lambda(max)) of the S130T mutant indicated a blue shift from that of the wild type in the absence and presence of chloride. For S130A, a large red shift (12 nm) in the absence of chloride was observed. The wild-type and all mutants showed the blue-shift of lambda(max) upon Cl(-) addition, from which the dissociation constants of Cl(-) were determined. The dissociation constants were 5, 89, 153 and 159 mM for the wild-type, S130A, S130T and S130C, respectively, at pH 7.0 and 25 degrees C. Circular dichroic spectra of the wild-type and the Ser-130 mutants exhibited an oligomerization. The present study revealed that the Ser-130 of N. pharaonis halorhodopsin is important for the chloride binding.

Amino Acid Sequence↗
PubMed2001

Light-induced structural changes occur in the transmembrane helices of the Natronobacterium pharaonis HtrII transducer.

The Natronobacterium pharaonis HtrII (NpHtrII) transducer interacts with its cognate photoactive sensory rhodopsin receptor, NpSRII, to mediate phototaxis responses. NpHtrII is predicted to have two transmembrane helices and a large cytoplasmic domain and to form a homodimer. Single cysteines were substituted into an engineered cysteine-less NpHtrII at 38 positions in its transmembrane domain. Oxidative disulfide cross-linking efficiencies of the monocysteine mutants were measured with or without photoactivation of NpSRII. The rapid cross-linking rates at several positions support that NpHtrII is a dimer when functionally expressed in the Halobacterium salinarum membrane. Thirteen positions in the second transmembrane segment (TM2) exhibited significant light-induced increases in cross-linking efficiency, and they define a single face traversing the length of the segment when modeled as an alpha-helix. Four positions in this helix showing light-induced decreases in efficiency are clustered on the cytoplasmic side of the protein. One of the monocysteine mutants, G83C, showed loss of phototaxis responses, and analysis of double mutants showed that the G83C mutation alters the dark structure of the TM2-TM2' region of NpHtrII. In summary, the results reveal conformationally active regions in the second transmembrane segment of NpHtrII and a face along the length of TM2 that becomes more available for TM2-TM2' cross-linking upon receptor photoactivation. The data also establish that one residue in TM2, Gly83, is critical for maintaining the proper conformation of NpHtrII for signal relay from the photoactivated receptor to the kinase-binding region of the transducer.

Amino Acid Sequence↗