Nucleotide sequence and transcription of the fbc operon from Rhodopseudomonas sphaeroides

Abstract

The fbc operon from Rhodopseudomonas sphaeroides encodes the three redox carriers of the ubiquinol‐cytochrome‐c reductase (b/c1 complex): FeS protein, cytochrome b and cytochrome c1 [Gabellini, N. et al. (1985) EMBO J. 2, 549‐553]. The nucleotide sequence of 3874 bp of cloned R. sphaeroides chromosomal DNA, including the three structural genes fbcF, fbcB and fbcC has been determined. The reading frames of the fbc genes could be identified readily since the encoded amino acid sequences are highly homologous with the sequences of the corresponding mitochondrial polypeptides. Initiation and termination points for transcription have been investigated by S1 nuclease protection analysis. The transcription of the fbc operon starts approximately 240 base pairs upstream from the start codon of the fbcF gene and terminates 120 base pairs downstream from the stop codon of the fbcC gene. Nucleotide sequences resembling recognition signals for the binding and release of the RNA polymerase were identified. The N‐terminal amino acid sequence of the mature cytochrome c1 was obtained by automated Edman degradation of the isolated subunit, confirming the fbcC reading frame and indicating that the bacterial pre‐apocytochrome c1 has a transient leader sequence including 21 residues. The N‐terminal sequence of one hydrophilic peptide of the FeS protein has been also obtained confirming the fbcF reading frame. The deduced amino acid sequences are discussed in relation to the known primary structures of the homologous proteins from mitochondria and chloroplasts. The primary structures of the polypeptides are evaluated with respect to (a) their topology in the membrane, (b) their biogenesis, (c) the structure of the catalytic sites and (d) subunit interactions.

Protein Sorting to Mitochondria: Evolutionary Conservations of Folding and Assembly

“…Both Paracoccus and Rhodobacter are probably close relatives to the endosymbiotic ancestor of mitochondria and contain in their plasma membranes or photosynthetic membranes, respectively, a bc, complex that is highly homologous to that in mitochondria (61). For example, the cytochrome cl of Rhodobacter capsulata is synthesized in the bacterial cytosol with a typical bacterial export signal that shows considerable similarity to the second part of the presequence of yeast cytochrome c1 (49,62) (Fig. 2).…”

Primary structure of cotranscribed genes encoding the Rieske Fe-S and cytochrome f proteins of the cyanobacterium Nostoc PCC 7906.

“…Fig. 4 shows an alignment of the Nostoc Rieske Fe-S protein sequence with the other currently available ones from spinach (17,18), photosynthetic purple bacteria (10,11), and mitochondria (ref. 21 conserved cysteine residues (positions 108 and 113).…”

“…In photosynthetic eukaryotes, the cytochromesf, b6, and subunit IV polypeptides are encoded by the chloroplast petA, -B, and -D genes, respectively; whereas, the gene petC encoding the -Rieske Fe-S protein is known to reside in the nucleus (7)(8)(9). In purple photosynthetic bacteria, contiguous genes named fbcFB, C (10) or petA,B,C (11) encode the three catalytic subunits (Rieske Fe-S protein, cytochrome b, and cytochrome c1, respectively) of the cytochrome b-c1 complex.…”

Kinetics of photosynthetic electron transfer in artificial vesicles reconstituted with purified complexes from Rhodobacter capsulatus

“…In order to place the cytochrome-cl heme at a distance comparable to that of cytochrome c2 on the same electron-transfer pathway, it would be necessary to dislocate cytochrome c1 over the RC complex. This would require considerable flexibility of the cytochromec1 apoprotein, which, on the other hand, is predominantly hydrophilic [48] and possibly protruding from the membrane. This conformational mobility is therefore in principle possible, a1 though no experimental evidence has been produced.…”