A transcription unit for the Rieske FeS-protein and cytochrome b in Chlorobium limicola

Michael Schütz*, Sabine Zirngibl, Johannes le Coutre, Michael Büttner, Dian Lin Xie, Nathan Nelson, Rainer Deutzmann, Günter Hauska

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


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 languageEnglish
Pages (from-to)163-174
Number of pages12
JournalPhotosynthesis Research
Issue number2
StatePublished - Feb 1994
Externally publishedYes


  • Green S-bacteria
  • cytochrome bc-complex
  • electron transport
  • membrane proteins
  • petB
  • petC


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