Selective lodo-Labeling of an Intrinsic Electron Donor of Photosystem II in Illuminated Tris-Treated Thylakoids

概要

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Peptides that participate in the oxidizing side of PS II were selectively tagged with iodine, activated by illuminated Tris-treated thylakoids. A peptide of 29 kDa was iodinated, with less labeling of 33- and 58-kDa peptides. The iodination was inhibited by DCMU, and suppressed when the Tris-treated thylakoids were supported by diphenylcarbazide. No peptide in the untreated thylakoids was iodinated. These findings indicate that the oxidation of I- at the oxidizing side of photosystem II results in iodination. The iodinated peptide of 29 kDa was identified to be one of the major components of the isolated PS II reaction center complex from the following characteristics of the peptide: 1) polymerization on heat-treatment (95℃, 5min) of the iodinated thylakoids in the presence of SDS and 2-mercaptoethanol, 2) thylakoid-binding after NaSCN-washing, and 3) migration distinct from that of the herbicide-binding protein in SDS-polyacrylamide gel electrophoresis. Thus, the iodinated 29-kDa peptide is a secondary electron donor of PS II or the nearest one to a site where I- is oxidized.
日本植物生理学会の論文