Photoaffinity labeling of an herbicide receptor protein in chloroplast membranes

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 78; no. 2; pp. 981 - 985
• Main Authors: Pfister, K, Steinback, K.E, Gardner, G, Arntzen, C.J
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 01.02.1981; National Acad Sciences
• Subjects: Binding sites; Biological Sciences: Botany; Chloroplasts; Electrons; Gels; Herbicides; P branes; Peas; Plants; Receptors; Thylakoids
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.78.2.981

2-Azido-4-ethylamino-6-isopropylamino-s-triazine (azido-atrazine) inhibits photosynthetic electron transport at a site identical to that affected by atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine). The latter is a well-characterized inhibitor of photosystem II reactions. Azido-atrazine was used as a photoaffinity label to identify the herbicide receptor protein; UV irradiation of chloroplast thylakoids in the presence of azido[14C]atrazine resulted in the covalent attachment of radioactive inhibitor to thylakoid membranes isolated from pea seedlings and from a triazine-susceptible biotype of the weed Amaranthus hybridus. No covalent binding of azido-atrazine was observed for thylakoid membranes isolated from a naturally occurring triazine-resistant biotype of A. hybridus. Analysis of thylakoid polypeptides from both the susceptible and resistant A. hybridus biotypes by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, followed by fluorography to locate14C label, demonstrated specific association of the azido [14C]atrazine with polypeptides of the 34- to 32-kilodalton size class in susceptible but not in resistant membranes.