Photooxidation of high-potential (c559, c556) and low-potential (c552) hemes in the cytochrome subunit of Rhodopseudomonas viridis reaction center. Characterization by FTIR spectroscopy.

The photooxidation of c559, c556 and c552 hemes in Rhodopseudomonas viridis cytochrome has been characterized by light-induced FTIR difference spectroscopy. Apart from the common features at 1659 cm-1 and 1561/1551 cm-1 which could arise from one (or possibly two) peptide bond(s), no evidence for major structural rearrangement of the polypeptide backbone was observed. A significant difference with respect to redox-induced FTIR spectra of cytochrome c is the absence of the Tyr marker at 1514/1518 cm-1 in Rps. viridis cytochrome, indicating that the localized shift of a Tyr side chain observed between ferro- and ferri-cytochrome c does not occur in Rps. viridis cytochrome.