Azidoatrazine: Photoaffinity Label for the Site of Triazine Herbicide Action in Chloroplasts

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Science  27 Feb 1981:
Vol. 211, Issue 4485, pp. 937-940
DOI: 10.1126/science.211.4485.937


Binding of the 4-azido analog of the herbicide atrazine to pea chloroplast membranes was compared with that of atrazine. When [14C]azidoatrazine was treated with 300-nanometer ultraviolet light in situ, reversibility of binding was lost in proportion to the duration of irradiation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of chloroplast membranes irradiated in the presence of [l4C]-azidoatrazine indicated radioactivity in only one region, corresponding to a protein with a molecular weight of approximately 32,000. Azidoatrazine is a photoaffinity reagent for the triazine binding site in chloroplasts and serves as a label to identify this site, which may be the apoprotein of the secondary electron acceptor in photosystem II.