Superoxide oxidase and reductase activity of cytochrome b559 in photosystem II.

摘要: This study provides evidence for the superoxide oxidase and reductase activity of cytochrome b(559) (cyt b(559)) in PSII. It is reported that Tris-treated PSII membranes upon illumination, both intermediate potential (IP) reduced high (HP(red)) forms cyt exhibit scavenging interconversion between IP HP(red) form. When were illuminated presence spin trap EMPO, formation anion radical (O(2)(*-)) was observed, as confirmed by EPR spin-trapping spectroscopy. The observations addition enzymatic (superoxide dismutase) non-enzymatic (cytochrome c, alpha-tocopherol Trolox) O(2)(*-) scavengers prevented light-induced conversion are oxidized O(2)(*-), respectively. Redox changes an exogenous source reconfirmed b(559). Furthermore, to form completely inhibited at pH>8 chemical modification imidazole ring histidine residues using diethyl pyrocarbonate. We proposed a change environment around heme iron, induced protonation deprotonation His(22) residue generates favorable condition oxidation reduction