Cytochrome c(6A) is a funnel for thiol oxidation in the thylakoid lumen.
Cytochrome c(6A) is a dithio-cytochrome recently discovered in land plants and green algae, and believed to be derived from the well-known cytochrome c(6). The function of cytochrome c(6A) is unclear. We propose that it catalyses the formation of disulphide bridges in thylakoid lumen proteins in a single-step disulphide exchange reaction, with subsequent transfer of the reducing equivalents to plastocyanin. The haem group of cytochrome c(6A) acts as an electron sink, allowing rapid resolution of a radical intermediate formed during reoxidation of cytochrome c(6A). Our model is consistent with previously published data on mutant plants, and the likely evolution of the protein.
Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
Beatrix G
BG
Schlarb-Ridley
Robert H
RH
Nimmo
Saul
S
Purton
Christopher J
CJ
Howe
Derek S
DS
Bendall
D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism*; D045365:Cytochromes c6 / Q000235:genetics / Q000378:metabolism*; D004220:Disulfides / Q000378:metabolism; D056890:Eukaryota / Q000378:metabolism*; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D010970:Plastocyanin / Q000235:genetics / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism*
D020418:Algal Proteins; D045365:Cytochromes c6; D004220:Disulfides; D010940:Plant Proteins; D013438:Sulfhydryl Compounds; D010970:Plastocyanin