The tryptic and chymotryptic fragments of the β-subunit of guanine nucleotide binding proteins in brain are identical to those of retinal transducin

AbstractThe 35-kDa β-subunit of transducin purified from rod outer segment membranes is cleaved into 2 major fragments by trypsin, and 7 major fragments by chymotrypsin. Identical fragments are visualized by immunoblotting with transducin-β specific antisera after proteolysis of rod outer segment membranes, purified brain guanine nucleotide binding proteins, and brain membranes. The results indicate that the β-subunits of transducin and of brain guanine nucleotide binding proteins are not only similar structurally, but are also similarly oriented in membranes with respect to accessibility to proteolytic enzymes