Biotinylation of transducin and G0 from bovine brain.

A method is described for modifying G proteins with biotin. With transducin, better results were obtained with the amino group-specific derivative BXNHS (biotinyl-epsilon-aminocaproic acid N-hydroxysuccinimide ester) as compared to the -SH-group specific reagent MBB (maleimidobutyrylbiocytin). Modification occurred under conditions preserving functional activity: Interaction of the biotinylated transducin with rod outer segment membranes was shown by its light-dependent association and by a GTP gamma S-binding assay. G0 from bovine brain was also biotinylated under conditions preserving its activity. Biotinyl-alpha 0 was shown to bind to a streptavidin Sepharose matrix. Biotinyl-G proteins, therefore, are proposed as tools for extracting proteins (receptors and effector systems), which interact under specific conditions with G proteins.