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PubMed1998

Basis for monomer stabilization in Rhodopseudomonas palustris cytochrome c' derived from the crystal structure.

The crystal structure of an unusual monomeric cytochrome c' from Rhodopseudomonas palustris (RPCP) has been determined at 2.3 A resolution. RPCP has the four-helix (helices A, B, C and D) bundle structure similar to dimeric cytochromes c'. However the amino acid composition of the surface of helices A and B in RPCP is remarkably different from that of the dimeric cytochromes c'. This surface forms the dimer interface in the latter proteins. RPCP has seven charged residues on this surface contrary to the dimeric cytochromes c', which have only two or three charged groups on the corresponding surface. Moreover, hydrophobic residues on this surface of RPCP are two to three times fewer than in dimeric cytochromes c'. As a result of the difference in amino acid composition, the A-B surface of RPCP is rather hydrophilic compared with dimeric cytochromes c'. We thus suggest that RPCP is monomeric in solution because of the hydrophilic nature of the A-B surface. The amino acid composition of the A-B surface is similar to that of Rhodobacter capsulatus cytochrome c' (RCCP), which is an equilibrium admixture of monomer and dimer. The charge distribution of the A-B surface in RCCP, however, is considerably different from that of RPCP. Due to the difference, RCCP can form dimers by both ionic and hydrophobic interactions. These dimers are quite different from those in proteins which form strong dimers such as in Chromatium vinosum, Rhodospirillum rubrum, Rhodospirillum molischianum and Alcaligenes. Cytochrome c' can be classified into two types. Type 1 cytochromes c' have hydrophobic A-B surfaces and they are globular. The A-B surface of type 2 cytochromes c' is hydrophilic and they take a monomeric or flattened dimeric form.

Amino Acid Sequence↗
PubMed1999

MAD structure of Pseudomonas nautica dimeric cytochrome c552 mimicks the c4 Dihemic cytochrome domain association.

The monohemic cytochrome c552from Pseudomonas nautica (c552-Pn) is thought to be the electron donor to cytochrome cd1, the so-called nitrite reductase (NiR). It shows as high levels of activity and affinity for the P. nautica NiR (NiR-Pn), as the Pseudomonas aeruginosa enzyme (NiR-Pa). Since cytochrome c552is by far the most abundant electron carrier in the periplasm, it is probably involved in numerous other reactions. Its sequence is related to that of the c type cytochromes, but resembles that of the dihemic c4cytochromes even more closely. The three-dimensional structure of P. nautica cytochrome c552has been solved to 2.2 A resolution using the multiple wavelength anomalous dispersion (MAD) technique, taking advantage of the presence of the eight Fe heme ions in the asymmetric unit. Density modification procedures involving 4-fold non-crystallographic averaging yielded a model with an R -factor value of 17.8 % (Rfree=20.8 %). Cytochrome c552forms a tight dimer in the crystal, and the dimer interface area amounts to 19% of the total cytochrome surface area. Four tighly packed dimers form the eight molecules of the asymmetric unit. The c552dimer is superimposable on each domain of the monomeric cytochrome c4from Pseudomomas stutzeri (c4-Ps), a dihemic cytochrome, and on the dihemic c domain of flavocytochrome c of Chromatium vinosum (Fcd-Cv). The interacting residues which form the dimer are both similar in character and position, which is also true for the propionates. The dimer observed in the crystal also exists in solution. It has been hypothesised that the dihemic c4-Ps may have evolved via monohemic cytochrome c gene duplication followed by evolutionary divergence and the adjunction of a connecting linker. In this process, our dimeric c552structure might be said to constitute a "living fossile" occurring in the course of evolution between the formation of the dimer and the gene duplication and fusion. The availability of the structure of the cytochrome c552-Pn and that of NiR from P. aeruginosa made it possible to identify putative surface patches at which the docking of c552to NiR-Pn may occur.

Amino Acid Sequence↗
PubMed1999

Taxon-specific content of oligonucleotide triplets in 16S rRNAs of anoxygenic phototrophic and nitrifying bacteria.

Theoretical evaluation of the content of oligonucleotide triplets AAA, CCC, and UAU in 16S rRNAs of anoxygenic phototrophic bacteria (genera Chlorobium; Chloroflexus; Chromatium: Rhodopseudomonas) and nitrifying bacteria (genera Nitrosococcus, Nitrosomonas, Nitrosolobus, Nitrosovibrio, Nitrospira, Nitrospina, Nitrobacter) showed that the number of the AAA, CCC or UAU triplets in 16S rRNAs specifically corresponds to the genus and species of bacteria. The ratio of AAA and CCC triplet numbers in the sequences of 16S rRNA (AAA/CCC) of anoxygenic phototrophic bacteria was within the range of 0.61 to 2.03, and the ratio of AAA and UAU (AAA/UAU) triplet numbers in the sequence of 16S rRNA was within the range of 2.88 to 12.00. The regions of any genus within the AAA/CCC and AAA/UAU axes did not overlap. The combination of the numbers of nucleotide triplets in 16S rRNA is genus-specific character. The similar data were obtained in the study of a physiological group of nitrifying bacteria. The range of AAA/UAU ratio was from 1.8 to 9.0, and range of AAA/CCC was from 0.9 to 2.6 for this taxon. The number of triplets in 16S rRNAs of the studied taxa was genus- and species-specific character. The biological significance of these data is the evidence that not only the sequence but the number of nucleotide triplets in 16S rRNAs reflects the phylogeny of corresponding taxa.

Bacteria↗
PubMed1993

Cloning and molecular analysis of the poly(3-hydroxybutyric acid) biosynthetic genes of Thiocystis violacea.

From a genomic library of Thiocystis violaceae strain 2311 in lambda L47, two adjacent EcoRI restriction fragments of 5361 base pairs (bp) and of 1978 bp were cloned. The 5361-bp EcoRI restriction fragment hybridized with a DNA fragment harbouring the Alcaligenes eutrophus poly(3-hydroxyalkanoate) (PHA) synthase operon (phbCAB) and restored the ability to synthesize and accumulate PHA in PHA-negative mutants derived from A. eutrophus. The nucleotide sequence analysis of both fragments revealed five open-reading frames (ORFs); at least three of them are probably relevant for PHA biosynthesis. The amino acid sequences of the putative proteins deduced from these genes indicate that they encode a beta-ketothiolase [phbATv, relative molecular mass (M(r)) 40850], which exhibited 87.3% amino acid identity with the beta-ketothiolase from Chromatium vinosum. The amino acid sequences of the putative proteins deduced from ORF2Tv (M(r) 41450) and phbCTv (M(r) 39550), which were located upstream of and antilinear to phbATv, exhibited 74.7% and 87.6% amino acid identity, respectively, with the corresponding gene products of C. vinosum. Downstream of and antilinear to phbCTv was located ORF5, which encodes for a protein of high relative molecular mass (M(r) 76428) of unknown function. With respect to the divergent organisation of ORF2Tv and phbCTv on one side and of phbATv on the other side and from the homologies of the putative gene products, this region of the T. violaceae genome resembled very much the corresponding region of C. vinosum, which was identified recently.

Amino Acid Sequence↗
PubMed1976

Cysteine and S-sulfocysteine biosynthesis in phototrophic bacteria.

Forteen species (17 strains) of phototrophic bacteria as well as one strain of Thiobacillus denitrificans were tested for cysteine synthase and S-sulfocysteine synthase. All strains contain cysteine sythase active with O-acetylserine; only the Chromatiaceae, two species of the Rhodospirillaceae and T. denitrificans contain S-sulfocysteine synthase. In six species repression by different sulfur compounds in the medium was studied. In Chromatium vinosum, cysteine synthase was found to be constitutive, while in the Rhodospirillaceae tested the enzyme is repressed by sulfide. Thiosulfate had a derepressive effect in Rhodopseudomonas globiformis but strongly repressed cysteine synthase in R. sulfidophila and R. palustris. Cysteine had only moderate effects with the species tested.

Cysteine↗
PubMed1995

Bacteriolytic activities of the free-living soil amoebae, Acanthamoeba castellanii, Acanthamoeba polyphaga and Hartmannella vermiformis.

Bacteriolytic activities of axenically grown free-living soil amoebae Acanthamoeba castellanii, Acanthamoeba polyphaga and Hartmannella vermiformis towards various Gram-positive and Gram-negative bacteria were determined. A spectrophotometric assay revealed that the specific bacteriolytic activities of both Acanthamoeba species were higher as those of the three Hartmannella strains. Bacillus megaterium, Bacillus subtilis, Chromatium vinosum, Micrococcus luteus and Pseudomonas fluorescens were more easily lysed than the other bacteria tested. Agrobacterium tumefaciens, Klebsiella aerogenes and Serratia marcescens were hardly affected at all by the amoebal bacteriolytic activities. Among the Gram-negative bacteria we observed differences in lysis sensitivity while the Gram-positive bacteria tested were sensitive to lysis. Isoelectric focusing (IEF) gel-electrophoresis in the pH range 3-10 was performed to separate the bacteriolytic isoenzymes of amoebae. Bacteriolytic patterns were shown by using an activity assay in which lysis bands were formed in the agar/bacteria gel-overlay. The activity assay revealed remarkable differences in typical banding patterns for bacteriolytic activities among amoebae. Distinct differences between typical pI points of bacteriolytic activities in Acanthamoeba and Hartmannella were shown. Bacteriolytic activities of Hartmannella were more pronounced and observed in the isoelectric points (pI) range of 4.0-9.3 while for Acanthamoeba the range was pI 4.5-8.9.

Acanthamoeba↗
PubMed1984

The stratified microbial community at Laguna Figueroa, Baja California, Mexico: a possible model for prephanerozoic laminated microbial communities preserved in cherts.

The microbial mat community of the evaporite flat at North Pond, Laguna Figueroa (Baja California, Mexico) was actively involved in the production of laminated sediments prior to 1978. Heavy rains in 1979 and 1980 flooded the mat with 1 and 3 meters of meteoric water respectively. The flooding deposited up to 10 cm of silicoclastic sediment over the Microcoleus-dominated mat and resulted in the cessation of laminated sediment deposition. In 1982, the surface had been recolonized by species of cyanobacteria (Spirulina, Oscillatoria) and purple photosynthetic bacteria (Chromatium, Thiocapsa). The silicoclastic sediments and residual evaporites, which overlaid the laminated sediment, had been reworked into an anaerobic, sulfide-rich mud and contained well preserved sheaths of filamentous and coccoid bacteria. The Swaziland Sequence in the Barberton mountain land (which includes the Onverwacht and Fig Tree Group as well as the Swartkoppie zone between them) contains laminated sediments and carbon-rich chert. Structurally preserved microfossils have been found in the smooth black chert but not in the laminae. We concur with others who suggested that the laminated sediments from the Swaziland Sequence were deposited by an active stratified microbial community. However, we propose that these organisms which were preserved were originally buried in the associated sulfide-rich muds and were subsequently silicified.

Bacteria↗
PubMed1998

Phylogenetic position of an obligately chemoautotrophic, marine hydrogen-oxidizing bacterium, Hydrogenovibrio marinus, on the basis of 16S rRNA gene sequences and two form I RuBisCO gene sequences.

Two form ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) genes from the obligately autotrophic, marine hydrogen oxidizer Hydrogenovibrio marinus were sequenced. The deduced amino acid sequences of both RuBisCOs revealed that they are similar to those of sulfur oxidizers (Thiobacillus) and a purple sulfur bacterium (Chromatium vinosum). According to the 16S rRNA gene sequences, H. marinus is also affiliated with these microorganisms, members of Thiomicrospira being the closest relatives. Sequence similarities of the 16S rRNA genes and of the RuBisCO genes among these gamma-Proteobacteria suggest a common autotrophic ancestry. An ancestor of purple sulfur bacteria might be a common root of H. marinus and related sulfur oxidizers.

Bacterial Proteins↗
PubMed1985

Amino acid sequence of high-redox-potential ferredoxin (HiPIP) isozymes from the extremely halophilic purple phototrophic bacterium, Ectothiorhodospira halophila.

The amino acid sequences of high-redox-potential ferredoxin (HiPIP) isozymes from Ectothiorhodospira halophila have been determined. These are: isozyme I, EPRAEDGHAHDYVNEAADPSHGRYQEGQLCENCAFWGEAVQDGWGRCTHPDFDEVLVKAEGWCSVYAPA S, and isozyme II, GLPDGVEDLPKAEDDHAHDYVNDAADTDHARFQEGQLCENCQFWVDYVNGWGYCQHPDFTDVLVRGEGW CSVYAPA. Isozyme II is the major form of HiPIP produced by the bacterium (65-80%) and is the most acidic of the known HiPIPs. The two isozymes are 72% identical to one another and require only a single residue deletion for alignment. Comparison of these HiPIPs with seven previously determined sequences revealed only 27% average identity. Both E. halophila HiPIP isozymes are likely to be functional since their sequences are equally distant from those of other species. The E. halophila HiPIP sequences show that H-bonding patterns recognized in Chromatium vinosum HiPIP are likely to be conserved and therefore cannot explain the unusually low redox potentials which have been reported.

Amino Acid Sequence↗
PubMed1985

The amino acid sequence of a high-redox-potential ferredoxin from the purple phototrophic bacterium, Rhodospirillum tenue strain 2761.

The 61-residue amino acid sequence of Rhodospirillum tenue, strain 2761, high-redox-potential ferredoxin (HiPIP) is GTNAAMRKAFNYQDTAKNGKCSGCAQFVPGASPTAAGGCKVIPGDNEIAPGGYCDAFIVKK. It differs from that of R. tenue strain 3761 by 16 amino acid substitutions plus two single-residue deletions. This 26% sequence difference is similar to that observed among separate species of chromatiaceae such as Chromatium vinosum, C. gracile, and Thiocapsa roseopersicina, and is suprising because there are no distinguishing microbiological characteristics separating these two R. tenue strains. The most interesting amino acid substitution in R. tenue 2761 HiPIP is Gly for Asn 45 (C. vinosum numbering). Besides the four cysteines required to bind the four iron-four sulfur cluster, only Tyr 19, Asn 45, and Gly 75 are absolutely conserved in the nine previously determined HiPIP sequences. If HiPIP is used as a measure of divergence of species, then R. tenue and C. vinosum are the most distant purple bacteria examined. Quite the opposite conclusion follows based on the sequences of the cytochromes c'. It is suggested that this anomaly is more likely owing to a change in function for HiPIP with subsequently rapid evolutionary change than to a relatively recent transfer of the cytochrome c' gene between species.

Amino Acid Sequence↗
PubMed1977

NMR characterization of three forms of ferredoxin from Desulphovibrio gigas, a sulphate reducer.

A NMR and magnetic susceptibility study of the oxidized and reduced states of three different oligomers (forms) of a [4Fe-4S] ferrodoxin protein from Desulphovibrio gigas, FdI, FdI', and FdII was carried out. FdI and FdI' are different trimers and FdII a tetramer of the same basic subunit. A probable assignment of the contact shifted resonances is indicated. Since the temperature dependences of the contact shifted responances associated with each [4Fe-4S] are not all similar a delocalized model for the spin densities on the 4Fe does not apply. The exchange rate between oxidized and reduced states is slow on the NMR time scale. The three oligomers are not magnetically equivalent. Using the "three state hypothesis" terminology it is shown that FdIox is predominantly in the C2- state and changes upon reduction into the C3- state, while FdIIox is in the C- state and changes into the C2- state. FdI' does not easily fit into this classification. This study shows a similarity of magnetic behaviour between FdI and bacterial ferredoxins (e.g. Bacillus polymyxa) and between FdII and HiPIP from Chromatium sp. The influence of the quaternary structure on the stabilization of the different oxidation states of ferredoxins as well as on their redox potentials is discussed.

Desulfovibrio↗
PubMed1980

Energy transfer and bacteriochlorophyll fluorescence in purple bacteria at low temperature.

Emission spectra of bacteriochlorophyll a fluorescence and absorption spectra of various purple bacteria were measured at temperatures between 295 and 4 K. For Rhodospirillum rubrum the relative yield of photochemistry was measured in the same temperature region. In agreement with earlier results, sharpening and shifts of absorption bands were observed upon cooling to 77 K. Below 77 K further sharpening occurred. In all species an absorption band was observed at 751-757 nm. The position of this band and its amplitude relative to the concentration of reaction centers indicate that this band is due to reaction center bacteriopheophytin. The main infrared absorption band of Rhodopseudomonas sphaeroides strain R26 is resolved in two bands at low temperature, which may suggest that there are two pigment-protein complexes in this species. Emission bands, like the absorption bands, shifted and sharpened upon cooling. The fluorescence yield remained constant or even decreased in some species between room temperature and 120 K, but showed an increased below 120 K. This increase was most pronounced in species, such as R. rubrum, which showed single banded emission spectra. In Chromatium vinosum three (835, 893 and 934 nm) and in Rps. sphaeroides two (888 and 909 nm) emission bands were observed at low temperature. The temperature dependence of the amplitudes of the short wavelength bands indicated the absence of a thermal equilibrium for the excitation energy distribution in C. vinosum and Rps. sphaeroides. In all species the increased in the yield was larger when all reaction centers were photochemically active than when the reaction centers were closed. In R. rubrum the increase in the fluorescence yield was accompanied by a decrease of the quantum yield of charge separation upon excitation of the antenna but not of the reaction center chlorophyll. Calculation of the Förster resonance integral at various temperatures indicated that the increase in fluorescence yield and the decrease in the yield of photochemistry may be due to a decrease in the rate of energy transfer between antenna bacteriochlorophyll molecules. The energy transfer from carotenoids to bacteriochlorophyll was independent of the temperature in all species examined. The results are discussed in terms of existing models for energy transfer in the antenna pigment system.

Bacteriochlorophylls↗
PubMed1981

The three-iron cluster in a ferredoxin from Desulphovibrio gigas. A low-temperature magnetic circular dichroism study.

Ferredoxin II from Desulphovibrio gigas is a tetrameric protein containing a novel iron-sulphur cluster consisting of three iron atoms. The low-temperature magnetic circular dichroism (MCD) spectra of the oxidized and dithionite-reduced forms of ferredoxin II have been measured over the wavelength range approx. 300-800 nm. Both oxidation levels of the cluster are shown to be paramagnetic, although only the oxidized form gives an EPR signal. MCD magnetization curves have been constructed over the temperature range approx. 1.5-150 K and at fields between 0 and 5.1 Tesla. The curve for the oxidized protein can be fitted to a ground state of spin S = 1/2 with an isotropic g factor of 2.01. There is evidence for the thermal population of a low-lying electronic state above 50 K. The reduced protein gives a distinctive set of magnetization curves that are tentatively assigned to a ground state of S = 2, with a predominantly axial zero-field distortion that leaves the doublet Ms = +/-2 lowest in energy. The zero-field components have a maximum energy spread of approx. 15 cm-1. which places an upper limit of 4 cm-1 on the axial zero-field parameter D. The MCD spectra of the oxidized and reduced forms of the cluster are quite distinctive from one another. The spectra of the oxidized state are also different from those of oxidized high-potential iron protein from Chromatium and should provide a useful criterion for distinguishing between four- and three-iron clusters in their highest oxidation levels.

Circular Dichroism↗
PubMed1991

Isolation and nucleotide sequence of the Thiobacillus ferrooxidans genes for the small and large subunits of ribulose 1,5-bisphosphate carboxylase/oxygenase.

The genes encoding for the large (rbcL) and small (rbcS) subunits of ribulose-1,5-bisphosphate carboxylase (RuBisCO) were cloned from the obligate autotroph Thiobacillus ferrooxidans, a bacterium involved in the bioleaching of minerals. Nucleotide sequence analysis of the cloned DNA showed that the two coding regions are separated by a 30-bp intergenic region, the smallest described for the RuBisCO genes. The rbcL and rbcS genes encode polypeptides of 473 and 118 amino acids, respectively. Comparison of the nucleotide and amino acid sequences with those of the genes for rbcL and rbcS found in other species demonstrated that the T. ferrooxidans genes have the closest degree of identity with those of Chromatium vinosum and of Alvinoconcha hessleri endosymbiont. Both T. ferrooxidans enzyme subunits contain all the conserved amino acids that are known to participate in the catalytic process or in holoenzyme assembly.

Amino Acid Sequence↗
PubMed1995

Characterization of the dynamic properties of Rhodobacter capsulatus ferricytochrome c'--a 28 kDa paramagnetic heme protein.

The cytochrome c' are paramagnetic heme proteins generally consisting of two identical 14 kDa subunits. The recent assignment of the 1H and 15N resonances of the Rhodobacter capsulatus ferricytochrome c' has allowed characterization of the dynamic properties by measurement of the heteronuclear NOE for each resolved amide group. The relative importance of fast local motion and paramagnetic effect on nuclear relaxation were distinguished by comparison of the measured heteronuclear NOE with that of the overall experimental average. We show that the average experimental value of -0.16 corresponds to the rigid body motion expected for a spherical complex of 28 kDa. Residues 3-5, 50-55 and 69-70 exhibit decreased heteronuclear NOE due to local motions on a fast time scale with respect to molecular tumbling. Based on the X-ray crystal structure of the homologous cytochrome c' from Chromatium vinosum, the mobile regions correspond to the N-terminus of helix-1 and 2 regions of nonregular secondary structure located between helices-2 and -3.

Amides↗
PubMed1992

Three-dimensional structure of the high-potential iron-sulfur protein isolated from the purple phototrophic bacterium Rhodocyclus tenuis determined and refined at 1.5 A resolution.

The molecular structure of the high-potential iron-sulfur protein (HiPIP) isolated from the phototrophic bacterium, Rhodocyclus tenuis, has been solved and refined to a nominal resolution of 1.5 A with a crystallographic R-factor of 17.3% for all measured X-ray data from 30 A to 1.5 A. It is the smallest of the HiPIP structures studied thus far with 62 amino acid residues. Crystals used in the investigation belonged to the space group P2(1) with unit cell dimensions of a = 36.7 A, b = 52.6 A, c = 27.6 A and beta = 90.8 degrees and contained two molecules per asymmetric unit. The structure was solved by a combination of multiple isomorphous replacement with two heavy-atom derivatives, anomalous scattering from the iron-sulfur cluster, symmetry averaging and solvent flattening. The folding motif for this HiPIP is characterized by one small alpha-helix, six Type I turns, an approximate Type II turn and one Type I' turn. As in other HiPIPs, the iron-sulfur cluster is co-ordinated by four cysteinyl ligands and exhibits a cubane-like motif. These cysteinyl ligands are all located in Type I turns. The hydrogen bonding around the metal cluster in the R. tenuis protein is similar to the patterns observed in the Chromatium vinosum and Ectothiorhodospira halophila HiPIPs. Several of the amino acid residues invariant in the previously determined C. vinosum and E. halophila structures are not retained in the R. tenuis molecule. There are 13 solvent molecules structurally conserved between the two R. tenuis HiPIP molecules in the asymmetric unit, some of which are important for stabilizing surface loops. Interestingly, while it is assumed that this HiPIP functions as a monomer in solution, the two molecules in the asymmetric unit pack as a dimer and are related to each other by an approximate twofold rotation axis.

Bacterial Proteins↗
PubMed1983

RNA ligase in bacteria: formation of a 2',5' linkage by an E. coli extract.

Ligase activity was detected in extracts of Escherichia coli, Clostridium tartarivorum, Rhodospirillum salexigens, Chromatium gracile, and Chlorobium limicola. Ligase was measured by joining of tRNA halves produced from yeast IVS-containing tRNA precursors by a yeast endonuclease. The structure of tRNATyr halves joined by an E. coli extract was examined. The ligated junction is resistant to nuclease P1 and RNAase T2 but sensitive to venom phosphodiesterase and alkaline hydrolysis, consistent with a 2',5' linkage. The nuclease-resistant junction dinucleotide comigrates with authentic (2',5') APA marker in thin-layer chromatography. The phosphate in the newly formed phosphodiester bond is derived from the pre-tRNA substrate. The widespread existence of a bacterial ligase raises the possibility of a novel class of RNA processing reactions.

Escherichia coli↗
PubMed1996

Spectroscopic characterization of nitrosylheme in nitric oxide complexes of ferric and ferrous cytochrome c' from photosynthetic bacteria.

Reactions of ferric and ferrous cytochromes c' from four photosynthetic bacteria (Rhodobacter capsulatus ATCC 11166, Rhodopseudomonas palustris ATCC 17001, Rhodospirillum rubrum ATCC 11170, and Chromatium vinosum ATCC 17899) with nitric oxide have been investigated by electronic absorption and electron paramagnetic resonance spectroscopies. The heme iron(III) of these ferric cytochromes c' has been recently reported to be in a quantum mechanically admixed (S = 5/2, 3/2) state [Fujii, S., Yoshimura, T., Kamada, H., Yamaguchi, K., Suzuki, S., Shidara, S. and Takakuwa, S. (1995) Biochim. Biophys. Acta 1251, 161-169]. The affinity of ferric cytochromes c' for NO among these bacterial species (C. vinosum > Rps. palustris approximately Rb. capsulatus >> R. rubrum) was apparently related to the S = 3/2 content in the or der. In the reaction of ferrous cytochrome c' with NO, six- and five-coordinated nitrosylhemes, which represent species with and without a ligand at the axial position trans to nitrosyl group, have been formed. The content of six-coordinated nitrosylheme in NO-ferrous cytochrome c' has been determined to be Rb. capsulatus approximately Rps. palustris > C. vinosum < R rubrum, suggesting that a stability of iron-to-histidine bond decreases with this order. The NO reactions of ferric and ferrous cytochromes c' from photosynthetic bacteria have been compared with those of cytochromes c' from denitrifying bacteria.

Cytochrome c Group↗