The GTPase actvating factor for transducin in rod photoreceptors is the complex between RGS9 and type 5 G protein beta subunit

摘要

Proteins of the regulators of G protein signaling (RGS) family modulate the duration of intracellular signaling by stimulating the GTPase activity of G protein alpha subunits. It has been established that the ninth member of the RGS family (RGS9) participates in accelerating the GTPase activity of t he photoreceptor-specific G protein, transducin. This process is essential for timely inactivation of the photo-transduction caseade during the recovery from a photoresponse. Here we report that functionally active RGS9 from vertebrate photoreceptors exists as a tight complex with the long splice variant of the G protein P subunit (Gp5L). RGS9 and G(beta5L) also form a complex when coexpressed in cell culture. Our data are consistent with the recent observation that severaI RGS proteins, including RGS9, contain G protein gamma-subunit like domain that can mediate their association with Gps (Snow B. E., Krumins, A. M., Brothers, G. M., Lee, S. F., WalI, M. A., Chung, S., Mangion, J., Arya, S., Gilman, A. G. & Siderovski, D. P. (1998) Proc. NatI. Acad. Sci. USA 95, l3307--l3312). We report an example of such a complex whose cellular localization and function are clearly defined.