Lack of association of Ca(2+)-calmodulin with the beta gamma-subunits of the photo-receptor G protein (transducin).
We previously reported that the beta gamma-subunit of transducin (T beta gamma) is 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. T beta gamma-2 enhances GTP binding to the alpha-subunit of transducin (T alpha) in the presence of a photobleaching intermediate of rhodopsin, while T beta gamma-1 is an inactive component with little enhancement ability (Fukada, Y., Ohguro, H., Saito, T., Yoshizawa, T., and Akino, T. (1989) J. Biol. Chem. 264: 5937-5943). To further elucidate the functional differences between T beta gamma-1 and T beta gamma-2, we examined the association of T beta gamma s with Ca(2+)-calmodulin, and the effect of Ca2+ on binding of GTP to T alpha in the presence of either T beta gamma-1 or T beta gamma-2. Ca2+ had no effect on the GTP binding activity of transducin and T beta gamma s could not associate with Ca(2+)-calmodulin, indicating that the relationship of T beta gamma with Ca(2+)-calmodulin of is different from that of the brain G protein.
Ohguro
H
H
Department of Ophthalmology, Sapporo Medical College, Japan.
Nakagawa
T
T
Kitamura
K
K
Akino
T
T
D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism*; D002417:Cattle; D002848:Chromatography, DEAE-Cellulose; D006160:Guanosine Triphosphate / Q000378:metabolism; D015293:Transducin / Q000378:metabolism*
D002147:Calmodulin; D006160:Guanosine Triphosphate; D015293:Transducin; D002118:Calcium