A specific beta gamma-subunit of transducin stimulates ADP-ribosylation of the alpha-subunit by pertussis toxin.
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.
Ohguro
H
H
Department of Biochemistry, Sapporo Medical College, Japan.
Fukada
Y
Y
Yoshizawa
T
T
Saito
T
T
Akino
T
T
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D002417:Cattle; D007700:Kinetics; D046911:Macromolecular Substances; D009243:NAD / Q000378:metabolism*; D037342:Pertussis Toxin; D012374:Rod Cell Outer Segment / Q000378:metabolism; D015293:Transducin / Q000302:isolation & purification / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D046911:Macromolecular Substances; D010566:Virulence Factors, Bordetella; D009243:NAD; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D015293:Transducin