Ohguro H, Fukada Y, Yoshizawa T, Saito T, Akino T
Department of Biochemistry, Sapporo Medical College, Japan.
Biochem Biophys Res Commun. 1990 Mar 30;167(3):1235-41. doi: 10.1016/0006-291x(90)90656-8.
Transducin (T alpha and T beta gamma) is a GTP-binding protein involved in the visual transduction process in a rod outer segment. We have previously demonstrated that T beta gamma is a mixture composed of two components, T beta gamma-1 and T beta gamma-2, with distinctive gamma-subunits, T gamma-1 and T gamma-2, respectively (Fukada et al., 1989, J. Biol. Chem., 264, 5937-5943). To investigate the interaction between T alpha and the two components of T beta gamma, the effect of either T beta gamma-1 or T beta gamma-2 on the ADP-ribosylation of T alpha catalyzed by pertussis toxin (IAP) was examined. T beta gamma-2 stimulated the ADP-ribosylation of T alpha by IAP, while T beta gamma-1 displayed almost no enhancement of the ADP-ribosylation. Addition of T beta gamma-1 to the mixture of T alpha and T beta gamma-2 had no effect on the ADP-ribosylation of T alpha. These results indicate that T alpha and T beta gamma-2 form a complex that serves as a substrate of IAP in the ADP-ribosylation reaction, while T beta gamma-1 has a little affinity for T alpha. It was suggested that T gamma-2 is an essential subunit for T beta to interact with T alpha.
