Reconstitution of Function in Fatty-Acid Inactivated Photosystem 2
Recent studies in our laboratory have reexamined the interaction of the unsaturated fatty acid, linolenic acid, with photosystem 2 and have documented two principal regions of inhibition: one associated with the donor complex (Signal 2f or D1) to the reaction center, and the other located on the reducing side between pheophytin and Qa (Golbeck, J.H. and Warden, J.T. (1984) Biochim. Biophys. Acta 767, 263-271). A further characterization of fatty acid inhibition of secondary electron transport in photosystem 2 at room temperature is presented. These studies demonstrate that linolenic acid, and related fatty acid analogs, (1) eliminate the transient absorption increase at 320 nm, attributed to Qa - and (2) abolish the photo-oxidation of the primary donor P680. Restoration of stable photochemistry, as evidenced by P680 + Qa - formation, can be effected by reconstitution with exogenous quinone. These data are consistent with the hypothesis that unsaturated fatty acids inhibit secondary electron transport in photosystem 2 via displacement of endogenous quinone from quinone-binding peptides.
KeywordsLinolenic Acid Unsaturated Fatty Acid Potassium Ferricyanide Elaidic Acid Bacterial Reaction Center
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