Abstract
A transcription unit petCB from Chlorobium limicola is described. The leading gene petC codes for a Rieske FeS-protein of 19.04 kDa with 181 amino acid residues. The following gene petB codes for a cytochrome b of 47.48 kDa with 428 amino acid residues. The transcription unit lacks a third gene pet-A for cytochrome c1 or-f, which is found in the fbc-operons of gram-negative bacteria. In the derived amino acid sequence for the Rieske FeS-protein the four cysteines and the 2 histidines are conserved in the peptides binding the 2Fe2S-cluster, although the redox potential of the cluster is about 150 mV more negative in Chlorobium. The gene for cytochrome b includes the coding region for an N-terminal, positively charged extension which is typical for Chlorobium. The gene is not split into two parts for cytochrome b6 and subunit IV. However, a fourteenth amino acid between the two histidines in the fourth, putative transmembrane helix, and the lack of an eighth transmembrane helix at the C-terminus, among other features, clearly resemble the cytochrome b6f-complexes. Therefore, the separation into b6f- and bc1-type complexes during evolution must have occurred before the split of the gene.
Original language | English |
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Pages (from-to) | 163-174 |
Number of pages | 12 |
Journal | Photosynthesis Research |
Volume | 39 |
Issue number | 2 |
DOIs | |
State | Published - Feb 1994 |
Externally published | Yes |
Keywords
- Green S-bacteria
- cytochrome bc-complex
- electron transport
- membrane proteins
- petB
- petC