Primary structure determination of two cytochromes c2: close similarity to functionally unrelated mitochondrial cytochrome C.

Abstract

The amino-acid sequences of the cytochromes c2 from the photosynthetic non-sulfur purple bacteria Rhodomicrobium vannielii and-Rhiodopseudomonas viridis have been determined. Only a single residue deletion (at position 11 in horse cytochrome c) is necessary to align the sequences with those of mitochondrial cytochromes c. The overall sequence similarity between these cytochromes c2 and mitochondrial cytochromes c is closer than that between mitochondrial cytochromes c and the other cytochromes c2 of known sequence, and in the latter multiple insertions and deletions must be postulated before a match can be obtained. Nevertheless, these two cytochromes c2 show no better reactivity with the mitochondrial cytochrome c oxidase than do the less well-matched cytochromes c2. The bearing of these findings on possible evolutionary relationship between mitochondria and prokaryotes is discussed.The non-sulfur purple bacteria (Rhodospirtllaceae) are a family of photosynthetic prokaryotes (1) which possess characteristic pigments and have the same type of metabolism. They share a unique ability to utilize a wide range of simple organic carbon sources and.some members can grow nonphotosynthetically under fully aerobic conditions. However, they do not exhibit a common morphology. Rhodomicrobium vanniehi resembles the nonphotosynthetic Hyphomicrobiaceae in that daughter cells are formed as spherical buds at the ends of filaments growing out from the mother cell. Rhodopseudomonas viridis also uses a budding mode of cell division, but lacks the stalked. and branched appearance of Rhodomicrobium. All but two of the remaining Rhodospirillaceae species, including rods, spirilla, and cocci, reproduce through binary fission.All Rhodospirillaceae produce large amounts of soluble c-type cytochrome when growing photosynthetically. The best-studied example is the cytochrome C2 from Rhodospirillum rubrum (2), for which both the amino-acid sequence (3) and three-dimensional structure (4) are known. R. rubrum cytochrome C2 has a strong structural resemblance to mitochondrial cytochrome c (5) and is more closely related in sequence to the eukaryotic proteins than are any of the other bacterial cytochromes examined (6) before now.In most species of Rhodospirillaceae, the predominant ctype cytochrome resembles R. rubrum cytochrome C2 in optical spectra, in oxidation-reduction potential (7), and in limited reactivity with beef heart cytochrome oxidase (8). This is true also (B. Errede and M. D. Kamen, unpublished) for the only soluble cytochromes found in Rm. vannielil and Rps. mrldis (10). In cells of R. rubrum, the cytochrome C2 can be photooxidized (11), but in Rps. mridis light-induced absorbance changes have been ascribed (10, 12) to a pair of particulate cytochromes (analogous to those of the purple sulfur bacterium Chromatium dinosum). § From whom reprints should be requested.We have been studying the amino-acid sequences of the Rhodospirillaceae cytochromes c2 and find that they can be divided at present into at least two groups ...

Sequence analysis and transcriptional organization of the Rhodopseudomonas viridis cytochrome c2 gene

“…The amino acid sequence predicted from this DNA sequence is in good agreement with the published R. viridis cytochrome c2 protein sequence (4,5). In addition, the DNA sequence indicates the existence of 20 extra Nterminal amino acid residues.…”

“…Two degenerate oligonucleotides, called 14merC2 and 17merC2, were synthesized on the basis of the published amino acid sequence of cytochrome c2 from R. viridis (5). Southern blot analysis of genomic DNA from R. viridis, digested with restriction enzyme PstI, resulted in hybridization of oligonucleotides 14merC2 and 17merC2 with an 8-kb DNA fragment (data not shown).…”

“…In addition, crystallizations of the cytochromes c2 from Rhodobacter sphaeroides (3), Rhodobacter capsulatus (21), and R. viridis (30) have been reported. All c2 cytochromes are closely related to the mitochondrial cytochrome c (5,36).…”

The Bradyrhizobium japonicum cycM gene encodes a membrane-anchored homolog of mitochondrial cytochrome c

“…Since the values found for CycM clearly fall within this range, they should allow us to classify the protein as a novel member of this group of c-type cytochromes, despite the presence of an N-terminal membrane anchor and, as a consequence, an internal rather than more N-terminal location of the heme-binding site. Besides CycM, cytochrome c2 from Rhodomicrobium vannielii and R. viridis were also found to be more similar to selected groups of mitochondrial cytochrome c than to other bacterial c-type cytochromes (2). These examples support the conclusion drawn from 16S rRNA analysis that the endosymbiont(s) that gave rise to mitochondria has to be placed in the a subdivision of the purple bacteria, which includes purple nonsulfur bacteria, rhizobia, agrobacteria, rickettsia, and several other chemotrophic genera not able to develop within eukaryotic cells (28,48,50).…”

The nitrite oxidizing system of Nitrobacter winogradskyi

“…The N. winogradskyi cytochrome c-550 is the most similar to eukaryotic cytochromes c among the non-photosynthetic bacterial cytochromes c so far known, and seems to resemble most Rhodopseudomonas viridis cytochrome c 2 [31] among cy-(A) N. winogradskyi [28] (B) Man [42] (C) S. cerevlstae [35,36) 1 10 20 30 Although Paracoccus denitrificans is assumed to be a candidate for the evolutionary origin of the mitochondrion [44] because its cytochrome c-550 is homologous to mitochondrial cytochrome c [30], its cytochrome c-550 belongs to L-type [45] unlike mitochondrial cytochrome c (M-type). On the basis of the findings that N. winogradskyi cytochrome c-550 belongs to M-type and is more homologous to mitochondrial cytochrome c than P. denitrificans cytochrome c-550, this bacterium may be a more appropriate candidate for the evolutionary origin of the mitochondrion.…”