Identification of the triazine receptor protein as a chloroplast gene product

K. E. Steinback, L. McIntosh, L. Bogorad, C. J. Arntzen

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Abstract

The triazine herbicides inhibit photosynthesis by blocking electron transport at the second stable electron acceptor of photosystem II. This electron transport component of chloroplast thylakoid membranes is a protein-plastoquinone complex termed 'B'. The polypeptide that is believed to be a component of the B complex has recently been identified as a 32- to 34-kilodalton polypeptide by using a photoaffinity labeling probe, azido-[14 C]atrazine. A 34-kilodalton polypeptide of pea chloroplasts rapidly incorporates [35S]methionine in vivo and is also a rapidly labeled product of chloroplast-directed protein synthesis. Trypsin treatment of membranes tagged with azido-[14C]atrazine, [35S]methionine in vivo, or [35S]methionine in isolated intact chloroplasts results in identical, sequential alterations of the 34-kilodalton polypeptide to species of 32, then 18 and 16 kilodaltons. From the identical pattern of susceptibility to trypsin we conclude that the rapidly synthesized 34-kilodalton polypeptide that is a product of chloroplast-directed protein synthesis is identical to the triazine herbicide-binding protein of photosystem II. Chloroplasts of both triazine-susceptible and triazine-resistant biotypes of Amaranthus hybridus synthesize the 34-kilodalton polypeptide, but that of the resistant biotype does not bind the herbicide.

Original languageEnglish (US)
Pages (from-to)7463-7467
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume78
Issue number12 II
StatePublished - Jan 1 1981

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