Fevzi Daldal | University of Pennsylvania (original) (raw)
Papers by Fevzi Daldal
The Phototrophic Prokaryotes, 1999
Photosynthesis: from Light to Biosphere, 1995
Photosynthesis: from Light to Biosphere, 1995
Photosynthesis: from Light to Biosphere, 1995
Journal of Molecular Biology, 2001
Recently, we demonstrated that the RegB/RegA two-component regulatory system from Rhodobacter cap... more Recently, we demonstrated that the RegB/RegA two-component regulatory system from Rhodobacter capsulatus functions as a global regulator of metabolic processes that either generate or consume reducing equivalents. For example, the RegB/RegA system controls expression of such energy generating processes as photosynthesis and hydrogen utilization. In addition, RegB/RegA also control nitrogen and carbon ®xation pathways that utilize reducing equivalents. Here, we use a combination of DNase I protection and plasmid-based reporter expression studies to demonstrate that RegA directly controls synthesis of cytochrome cbb 3 and ubiquinol oxidases that function as terminal electron acceptors in a branched respiratory chain. We also demonstrate that RegA controls expression of cytochromes c 2 , c y, and the cytochrome bc 1 complex that are involved in both photosynthetic and respiratory electron transfer events. These data provide evidence that the RegB/RegA two-component system has a major role in controlling the synthesis of numerous processes that affect reducing equivalents in Rhodobacter capsulatus.
Trends in Microbiology, 2000
Research in Microbiology, 2005
Cells of the facultative photosynthetic bacterium Rhodobacter capsulatus (MT1131 strain) incubate... more Cells of the facultative photosynthetic bacterium Rhodobacter capsulatus (MT1131 strain) incubated with 10 µg ml −1 of the toxic oxyanion tellurite (TeO 2− 3 ) exhibited an increase in superoxide dismutase activity. The latter effect was also seen upon incubation with sublethal amounts of paraquat, a cytosolic generator of superoxide anions (O ·− 2 ), in parallel with a strong increase in tellurite resistance (Te R ). A mutant strain (CW10) deficient in SenC, a protein with similarities to peroxiredoxin/thiol:disulfide oxidoreductases and a homologue of mitochondrial Sco proteins, was constructed by interposon mutagenesis via the gene transfer agent system. Notably, the absence of SenC affected R. capsulatus resistance to periplasmic O ·− 2 generated by xanthine/xanthine oxidase but not to cytosolic O ·− 2 produced by paraquat. Further, the absence of SenC did not affect R. capsulatus tellurite resistance. We conclude that: (1) cytosolic-generated O ·− 2 enhances Te R of this bacterial species;
Archives of Microbiology, 1992
(1) The electron transport system of heterotrophically dark-grown Rhodobacter capsulatus was inve... more (1) The electron transport system of heterotrophically dark-grown Rhodobacter capsulatus was investigated using the wild-type strain MT1131 and the phototrophic non-competent (Ps-) mutant MT-GS18 carrying deletions of the genes for cytochrome c1 and b of the bc1 complex and for cytochrome c2. (2) Spectroscopic and thermodynamic data demonstrate that deletion of both bc1 complex and cyt. c2 still leaves several
Archives of Microbiology, 1993
Biochemistry, 1993
The hydroubiquinone-cytochrome c2 oxidoreductase (cyt bcl) from Rhodobacter capsulatus has been s... more The hydroubiquinone-cytochrome c2 oxidoreductase (cyt bcl) from Rhodobacter capsulatus has been solubilized according to the dodecyl maltoside method and isolated, and its minimal functional composition has been characterized. We find the complex to be composed of three protein subunits corresponding to polypeptides of cyt b (44 kDa), cyt C I (33 kDa), and 2Fe2S cluster (24 kDa). A fourth band sometimes discernable at 22 kDa appears to be an artifact of the polyacrylamide gel electrophoresis procedure. Its appearance is shown to be derived from the 2Fe2S cluster subunit by the similarity of the binding of subunit-specific monoclonal antibodies and the identical N-terminal sequence of the 24-and 22-kDa bands. The cofactors of cyt bcl, namely, cyt bH, cyt bL, cyt c1, and the 2Fe2S center, the Qm and Qow domains of the Qo site, and the Qi site appear intact as indicated by their optical and EPR spectral signatures, redox properties, and inhibitor binding. The electron paramagnetic resonance spectrum of the cyt bH heme is altered by antimycin, consistent with a change in the dihedral angle between the ligating histidine imidazoles, while the spectrum of the cyt bL heme is broadened by stigmatellin. The ubiquinone-10 content is variable, ranging from 0.8 to 3 molecules/cyt bcl. Activity studies define this three-subunit cyt bcl complex as a minimal structure, equipped as the enzyme in the native state and capable of full catalytic activity.
Biochemistry, 1992
The Rieske protein of the ubiquinol-cytochrome c oxidoreductase (bc1 complex or b6f complex) cont... more The Rieske protein of the ubiquinol-cytochrome c oxidoreductase (bc1 complex or b6f complex) contains a [2Fe-2S] cluster which is thought to be bound to the protein via two nitrogen and two sulfur ligands [Britt, R. D., Sauer, K., Klein, M. P., Knaff, D. B., Kriauciunas, A., Yu, C.-A., Yu, L., & Malkin, R. (1991) Biochemistry 30, 1892-1901; Gurbiel, R. J., Ohnishi, T., Robertson, D. E., Daldal, F., & Hoffman, B. M. (1991) Biochemistry 30, 11579-11584]. All available Rieske amino acid sequences have carboxyl termini featuring two conserved regions containing four cysteine (Cys) and two or three histidine (His) residues. Site-directed mutagenesis was applied to the Rieske protein of the photosynthetic bacterium Rhodobacter capsulatus, and the mutants obtained were studied biochemically in order to identify which of these conserved residues are the ligands of the [2Fe-2S] cluster. It was found that His159 (in the R. capsulatus numbering) is not a ligand and that the presence of the Rieske protein in the intracytoplasmic membrane is greatly decreased by alteration of any of the remaining six His or Cys residues. Among these mutations, only the substitution Cys155 to Ser resulted in the synthesis of Rieske protein (in a small amount) which contained a [2Fe-2S] cluster with altered biophysical properties. This finding suggested that Cys155 is not a ligand to the cluster. A comparison of the conserved regions of the Rieske proteins with bacterial aromatic dioxygenases (which contain a spectrally and electrochemically similar [2Fe-2S] cluster) indicated that Cys133, His135, Cys153, and His156 are conserved in both groups of enzymes, possibly as ligands to their [2Fe-2S] clusters. These findings led to the proposal that Cys138 and Cys155, which are not conserved in bacterial dioxygenases, may form an internal disulfide bond which is important for the structure of the Rieske protein and the conformation of the quinol oxidation (Qo) site of the bc1 complex.
Biochemistry, 1990
Seven single-site mutants in six residues of the cyt b polypeptide of Rhodobacter capsulatus sele... more Seven single-site mutants in six residues of the cyt b polypeptide of Rhodobacter capsulatus selected for resistance to the Q, site inhibitors stigmatellin, myxothiazol, or mucidin [Daldal, F., Tokito, M. K., Davidson, E,, & Faham, M. (1989) EMBO J. 8, 3951-39611 have been characterized by using optical and EPR spectroscopy and single-turnover kinetic analysis. The strains were compared with wild-type strain MTl131 and with the Psstrain R126 (G158D), which is dysfunctional in its Q, site [Robertson, D. E., Davidson, E., Prince, R. C . , van den Berg, W. H., Marrs, B. L., & Dutton, P. L. (1986) J. Biol. Chem. 261, 584-5911. Mutants selected for stigmatellin resistance induced a weakening in the binding of the inhibitor without discernible loss of ubiquinone(Q)/ubiquinol(QH2) binding affinity to the Q, site or kinetic impairment to catalysis. Mutants selected for myxothiazol or mucidin resistance, inducing weakening of inhibitor binding, all displayed impaired rates of Q, site catalysis: The most severe cases (F144L, F144S) displayed loss of affinity for Q, and evidence suggests that parallel loss of affinity for the substrate QH2 was incurred in these strains. The results provide a view of the nature of the interaction of Q and QH2 of the Qwi with the Q, site. Consideration of the mutational substitutions and their structural positions along with comparisons with the QA and QB sites of the photosynthetic reaction center suggests a model for the structure of the Q, site.
Journal of Molecular Biology, 1987
Detailed comparison of the 'Rhodopseudomonas sphaeroides GA' strain used by with genuine R. sphae... more Detailed comparison of the 'Rhodopseudomonas sphaeroides GA' strain used by with genuine R. sphaeroides and R. capsulata strains indicated that the previously reported j'bc operon of R. sphaeroides (Gabellini and Sebald, 1986) encoding the structural genes for the Rieske Fe-S protein, cytochrome b and cytochrome c1 subunits of the ubiquinol : cytochrome c2 oxidoreductase, is not from R. sphaeroides, but is rather from a strain of R. capsulata. Consequently, the genuine be, genes from R. sphaeroides were cloned using corresponding R. capsulata genes as probes, and a partial nucleotide sequence for the Rieske Fe-S protein of R. sphaeroides was determined and compared with that, of R. capsulata.
Gene, 1984
The nucleotide sequence of a 1.3-kb DNA fragment containing the entire pfkB gene which codes for ... more The nucleotide sequence of a 1.3-kb DNA fragment containing the entire pfkB gene which codes for Pfk-2 of Escherichia coli, a minor phosphofructokinase (Pfk) enzyme, is reported. The Pfk-2 protein subunit is encoded by 924 bp, has 308 amino acids and an Mr of 33 000. Like other weakly expressed E. coli genes the codon usage in the pfkB gene is random; there is no strong bias for the usage of major tRNA isoaccepting species, and the codon preference rules of Grosjean and Fiers [Gene, 18 (1982) 199-209] are followed. This is the first report of the complete gene sequence of a phosphofructokinase.
Biochimica Et Biophysica Acta-bioenergetics, 1987
The nature and number of physiological electron donors to the photochemical reaction center of Rh... more The nature and number of physiological electron donors to the photochemical reaction center of Rhodobacter capsulatus have been probed by deleting the genes for cytochromes c1 and b of the cytochrome bc1 complex, alone or in combination with deletion of the gene for cytochrome c2. Deletion of cytochrome c1 renders the organism incapable of photosynthetic growth, regardless of the presence or absence of cytochrome c2, because in the absence of the bc1 complex there is no cyclic electron transfer, nor any alternative source of electrons to rereduce the photochemically oxidized reaction center. While cytochrome c2 is capable of reducing the reaction center, there appears no alternative route for its rereduction other than the bc1 complex. The deletion of cytochromes c1 and c2 reveals previously unrecognized membrane-bound and soluble high potential c-type cytochromes, with Em7 = +312 mV and Em6.5 = +316 mV, respectively. These cytochromes do not donate electrons to the reaction center, and their roles are unknown.
Journal of Molecular Biology, 1987
Biochimica Et Biophysica Acta-bioenergetics, 1987
ABSTRACT MT113, a nonphotosynthetic mutant of Rhodobacter capsulatus previously characterized as ... more ABSTRACT MT113, a nonphotosynthetic mutant of Rhodobacter capsulatus previously characterized as lacking cytochrome c2 is shown to lack also cytochrome c1, the Rieske iron-sulfur cluster and the antimycin sensitive semiquinone Q⨪c, all components of the cytochrome bc1 complex. Although MT113 contained b-type cytochromes and other iron-sulfur clusters at nearly wild-type level, it lacks c-type cytochromes. Based on antibody detection, c2 apoprotein was absent in MT113, however the apoproteins corresponding to the cytochromes b and c1 and the Rieske iron-sulfur cluster were present in reduced amounts. Genetic analysis indicated that the lesion appears to be due to a single mutation which is not localized in the structural genes of cytochrome c2 or the bc1 complex. These data taken together suggest that the pleiotropic mutation in MT113 might be related to the biosynthesis of c-type cytochromes.
Journal of Molecular Biology, 1987
The nucleotide sequence of the pet operon of Rhodopseudomonas capsulata strain SB1003 has been de... more The nucleotide sequence of the pet operon of Rhodopseudomonas capsulata strain SB1003 has been determined. This operon consists of the petA, petB and petC genes, which encode the Rieske Fe-S protein, cytochrome b and cytochrome cl, respectively, all components of the ubiquinol-cytochrome c2 oxidoreductase. The deduced amino acid sequences of the pet genes show homology to the corresponding proteins from other organisms, and particularly high homologies (over 90% for amino acid and nucleotide sequences) to the previously described fbc operon from a strain previously identified as Rhodopseudomonas spheroides GA. The amino acid sequences of the pet proteins are discussed with reference to the structure and function of the ubiquinol-cytochrome c1 oxidoreductase.
Journal of Bacteriology, 2001
The Phototrophic Prokaryotes, 1999
Photosynthesis: from Light to Biosphere, 1995
Photosynthesis: from Light to Biosphere, 1995
Photosynthesis: from Light to Biosphere, 1995
Journal of Molecular Biology, 2001
Recently, we demonstrated that the RegB/RegA two-component regulatory system from Rhodobacter cap... more Recently, we demonstrated that the RegB/RegA two-component regulatory system from Rhodobacter capsulatus functions as a global regulator of metabolic processes that either generate or consume reducing equivalents. For example, the RegB/RegA system controls expression of such energy generating processes as photosynthesis and hydrogen utilization. In addition, RegB/RegA also control nitrogen and carbon ®xation pathways that utilize reducing equivalents. Here, we use a combination of DNase I protection and plasmid-based reporter expression studies to demonstrate that RegA directly controls synthesis of cytochrome cbb 3 and ubiquinol oxidases that function as terminal electron acceptors in a branched respiratory chain. We also demonstrate that RegA controls expression of cytochromes c 2 , c y, and the cytochrome bc 1 complex that are involved in both photosynthetic and respiratory electron transfer events. These data provide evidence that the RegB/RegA two-component system has a major role in controlling the synthesis of numerous processes that affect reducing equivalents in Rhodobacter capsulatus.
Trends in Microbiology, 2000
Research in Microbiology, 2005
Cells of the facultative photosynthetic bacterium Rhodobacter capsulatus (MT1131 strain) incubate... more Cells of the facultative photosynthetic bacterium Rhodobacter capsulatus (MT1131 strain) incubated with 10 µg ml −1 of the toxic oxyanion tellurite (TeO 2− 3 ) exhibited an increase in superoxide dismutase activity. The latter effect was also seen upon incubation with sublethal amounts of paraquat, a cytosolic generator of superoxide anions (O ·− 2 ), in parallel with a strong increase in tellurite resistance (Te R ). A mutant strain (CW10) deficient in SenC, a protein with similarities to peroxiredoxin/thiol:disulfide oxidoreductases and a homologue of mitochondrial Sco proteins, was constructed by interposon mutagenesis via the gene transfer agent system. Notably, the absence of SenC affected R. capsulatus resistance to periplasmic O ·− 2 generated by xanthine/xanthine oxidase but not to cytosolic O ·− 2 produced by paraquat. Further, the absence of SenC did not affect R. capsulatus tellurite resistance. We conclude that: (1) cytosolic-generated O ·− 2 enhances Te R of this bacterial species;
Archives of Microbiology, 1992
(1) The electron transport system of heterotrophically dark-grown Rhodobacter capsulatus was inve... more (1) The electron transport system of heterotrophically dark-grown Rhodobacter capsulatus was investigated using the wild-type strain MT1131 and the phototrophic non-competent (Ps-) mutant MT-GS18 carrying deletions of the genes for cytochrome c1 and b of the bc1 complex and for cytochrome c2. (2) Spectroscopic and thermodynamic data demonstrate that deletion of both bc1 complex and cyt. c2 still leaves several
Archives of Microbiology, 1993
Biochemistry, 1993
The hydroubiquinone-cytochrome c2 oxidoreductase (cyt bcl) from Rhodobacter capsulatus has been s... more The hydroubiquinone-cytochrome c2 oxidoreductase (cyt bcl) from Rhodobacter capsulatus has been solubilized according to the dodecyl maltoside method and isolated, and its minimal functional composition has been characterized. We find the complex to be composed of three protein subunits corresponding to polypeptides of cyt b (44 kDa), cyt C I (33 kDa), and 2Fe2S cluster (24 kDa). A fourth band sometimes discernable at 22 kDa appears to be an artifact of the polyacrylamide gel electrophoresis procedure. Its appearance is shown to be derived from the 2Fe2S cluster subunit by the similarity of the binding of subunit-specific monoclonal antibodies and the identical N-terminal sequence of the 24-and 22-kDa bands. The cofactors of cyt bcl, namely, cyt bH, cyt bL, cyt c1, and the 2Fe2S center, the Qm and Qow domains of the Qo site, and the Qi site appear intact as indicated by their optical and EPR spectral signatures, redox properties, and inhibitor binding. The electron paramagnetic resonance spectrum of the cyt bH heme is altered by antimycin, consistent with a change in the dihedral angle between the ligating histidine imidazoles, while the spectrum of the cyt bL heme is broadened by stigmatellin. The ubiquinone-10 content is variable, ranging from 0.8 to 3 molecules/cyt bcl. Activity studies define this three-subunit cyt bcl complex as a minimal structure, equipped as the enzyme in the native state and capable of full catalytic activity.
Biochemistry, 1992
The Rieske protein of the ubiquinol-cytochrome c oxidoreductase (bc1 complex or b6f complex) cont... more The Rieske protein of the ubiquinol-cytochrome c oxidoreductase (bc1 complex or b6f complex) contains a [2Fe-2S] cluster which is thought to be bound to the protein via two nitrogen and two sulfur ligands [Britt, R. D., Sauer, K., Klein, M. P., Knaff, D. B., Kriauciunas, A., Yu, C.-A., Yu, L., & Malkin, R. (1991) Biochemistry 30, 1892-1901; Gurbiel, R. J., Ohnishi, T., Robertson, D. E., Daldal, F., & Hoffman, B. M. (1991) Biochemistry 30, 11579-11584]. All available Rieske amino acid sequences have carboxyl termini featuring two conserved regions containing four cysteine (Cys) and two or three histidine (His) residues. Site-directed mutagenesis was applied to the Rieske protein of the photosynthetic bacterium Rhodobacter capsulatus, and the mutants obtained were studied biochemically in order to identify which of these conserved residues are the ligands of the [2Fe-2S] cluster. It was found that His159 (in the R. capsulatus numbering) is not a ligand and that the presence of the Rieske protein in the intracytoplasmic membrane is greatly decreased by alteration of any of the remaining six His or Cys residues. Among these mutations, only the substitution Cys155 to Ser resulted in the synthesis of Rieske protein (in a small amount) which contained a [2Fe-2S] cluster with altered biophysical properties. This finding suggested that Cys155 is not a ligand to the cluster. A comparison of the conserved regions of the Rieske proteins with bacterial aromatic dioxygenases (which contain a spectrally and electrochemically similar [2Fe-2S] cluster) indicated that Cys133, His135, Cys153, and His156 are conserved in both groups of enzymes, possibly as ligands to their [2Fe-2S] clusters. These findings led to the proposal that Cys138 and Cys155, which are not conserved in bacterial dioxygenases, may form an internal disulfide bond which is important for the structure of the Rieske protein and the conformation of the quinol oxidation (Qo) site of the bc1 complex.
Biochemistry, 1990
Seven single-site mutants in six residues of the cyt b polypeptide of Rhodobacter capsulatus sele... more Seven single-site mutants in six residues of the cyt b polypeptide of Rhodobacter capsulatus selected for resistance to the Q, site inhibitors stigmatellin, myxothiazol, or mucidin [Daldal, F., Tokito, M. K., Davidson, E,, & Faham, M. (1989) EMBO J. 8, 3951-39611 have been characterized by using optical and EPR spectroscopy and single-turnover kinetic analysis. The strains were compared with wild-type strain MTl131 and with the Psstrain R126 (G158D), which is dysfunctional in its Q, site [Robertson, D. E., Davidson, E., Prince, R. C . , van den Berg, W. H., Marrs, B. L., & Dutton, P. L. (1986) J. Biol. Chem. 261, 584-5911. Mutants selected for stigmatellin resistance induced a weakening in the binding of the inhibitor without discernible loss of ubiquinone(Q)/ubiquinol(QH2) binding affinity to the Q, site or kinetic impairment to catalysis. Mutants selected for myxothiazol or mucidin resistance, inducing weakening of inhibitor binding, all displayed impaired rates of Q, site catalysis: The most severe cases (F144L, F144S) displayed loss of affinity for Q, and evidence suggests that parallel loss of affinity for the substrate QH2 was incurred in these strains. The results provide a view of the nature of the interaction of Q and QH2 of the Qwi with the Q, site. Consideration of the mutational substitutions and their structural positions along with comparisons with the QA and QB sites of the photosynthetic reaction center suggests a model for the structure of the Q, site.
Journal of Molecular Biology, 1987
Detailed comparison of the 'Rhodopseudomonas sphaeroides GA' strain used by with genuine R. sphae... more Detailed comparison of the 'Rhodopseudomonas sphaeroides GA' strain used by with genuine R. sphaeroides and R. capsulata strains indicated that the previously reported j'bc operon of R. sphaeroides (Gabellini and Sebald, 1986) encoding the structural genes for the Rieske Fe-S protein, cytochrome b and cytochrome c1 subunits of the ubiquinol : cytochrome c2 oxidoreductase, is not from R. sphaeroides, but is rather from a strain of R. capsulata. Consequently, the genuine be, genes from R. sphaeroides were cloned using corresponding R. capsulata genes as probes, and a partial nucleotide sequence for the Rieske Fe-S protein of R. sphaeroides was determined and compared with that, of R. capsulata.
Gene, 1984
The nucleotide sequence of a 1.3-kb DNA fragment containing the entire pfkB gene which codes for ... more The nucleotide sequence of a 1.3-kb DNA fragment containing the entire pfkB gene which codes for Pfk-2 of Escherichia coli, a minor phosphofructokinase (Pfk) enzyme, is reported. The Pfk-2 protein subunit is encoded by 924 bp, has 308 amino acids and an Mr of 33 000. Like other weakly expressed E. coli genes the codon usage in the pfkB gene is random; there is no strong bias for the usage of major tRNA isoaccepting species, and the codon preference rules of Grosjean and Fiers [Gene, 18 (1982) 199-209] are followed. This is the first report of the complete gene sequence of a phosphofructokinase.
Biochimica Et Biophysica Acta-bioenergetics, 1987
The nature and number of physiological electron donors to the photochemical reaction center of Rh... more The nature and number of physiological electron donors to the photochemical reaction center of Rhodobacter capsulatus have been probed by deleting the genes for cytochromes c1 and b of the cytochrome bc1 complex, alone or in combination with deletion of the gene for cytochrome c2. Deletion of cytochrome c1 renders the organism incapable of photosynthetic growth, regardless of the presence or absence of cytochrome c2, because in the absence of the bc1 complex there is no cyclic electron transfer, nor any alternative source of electrons to rereduce the photochemically oxidized reaction center. While cytochrome c2 is capable of reducing the reaction center, there appears no alternative route for its rereduction other than the bc1 complex. The deletion of cytochromes c1 and c2 reveals previously unrecognized membrane-bound and soluble high potential c-type cytochromes, with Em7 = +312 mV and Em6.5 = +316 mV, respectively. These cytochromes do not donate electrons to the reaction center, and their roles are unknown.
Journal of Molecular Biology, 1987
Biochimica Et Biophysica Acta-bioenergetics, 1987
ABSTRACT MT113, a nonphotosynthetic mutant of Rhodobacter capsulatus previously characterized as ... more ABSTRACT MT113, a nonphotosynthetic mutant of Rhodobacter capsulatus previously characterized as lacking cytochrome c2 is shown to lack also cytochrome c1, the Rieske iron-sulfur cluster and the antimycin sensitive semiquinone Q⨪c, all components of the cytochrome bc1 complex. Although MT113 contained b-type cytochromes and other iron-sulfur clusters at nearly wild-type level, it lacks c-type cytochromes. Based on antibody detection, c2 apoprotein was absent in MT113, however the apoproteins corresponding to the cytochromes b and c1 and the Rieske iron-sulfur cluster were present in reduced amounts. Genetic analysis indicated that the lesion appears to be due to a single mutation which is not localized in the structural genes of cytochrome c2 or the bc1 complex. These data taken together suggest that the pleiotropic mutation in MT113 might be related to the biosynthesis of c-type cytochromes.
Journal of Molecular Biology, 1987
The nucleotide sequence of the pet operon of Rhodopseudomonas capsulata strain SB1003 has been de... more The nucleotide sequence of the pet operon of Rhodopseudomonas capsulata strain SB1003 has been determined. This operon consists of the petA, petB and petC genes, which encode the Rieske Fe-S protein, cytochrome b and cytochrome cl, respectively, all components of the ubiquinol-cytochrome c2 oxidoreductase. The deduced amino acid sequences of the pet genes show homology to the corresponding proteins from other organisms, and particularly high homologies (over 90% for amino acid and nucleotide sequences) to the previously described fbc operon from a strain previously identified as Rhodopseudomonas spheroides GA. The amino acid sequences of the pet proteins are discussed with reference to the structure and function of the ubiquinol-cytochrome c1 oxidoreductase.
Journal of Bacteriology, 2001