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.