BINDING OF A PHOTOREACTIVE PYRETHROID TO BETA-SUBUNIT OF GTP-BINDING PROTEINS

Visual cycle signal transduction components and purified bovine brain GTP-binding proteins (G-proteins) have been used to study the possibility that pyrethroids interact with signal-transducing G-proteins. A photoactivatable arylazide derivative of fenvalerate ([3H]decyanoazidofenvalerate or [3H]DeCAF) has been used to photoaffinity label proteins in homogenized bovine retina, rod outer segments (ROS), and purified transducin-the retinal signal transducing G-protein-as well as the βγ subunit of G-proteins purified from bovine brain. All displayed [3H]DeCAF labeling to a 36-kDa protein. GTPγS treatment of ROS displaced labeling from membrane-bound protein(s) to a soluble fraction. [3H]DeCAF labeling of 36-kDa proteins was specific and saturable and greatest specific activity was obtained with purified transducin or β subunit of bovine brain G-proteins. Purified [3H]DeCAF-labeled β subunit of transducin (Tβ) was identified by immunoprecipitation with antibodies directed against Tβ or a synthetic peptide from Tβ. Treatment of ROS membranes by DeCAF resulted in stimulation of release of α subunit of transducin, as measured by [32P]ADP-ribosylation. These data complement previously published results and indicate that pyrethroids bind to the β subunit of G-proteins and modify their interaction with the α subunit. © 1991.