The GTPase activating factor for transducin in rod photoreceptors is the complex between RGS9 and type 5 G protein beta subunit.
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 the photoreceptor-specific G protein, transducin. This process is essential for timely inactivation of the phototransduction cascade 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 beta subunit (Gbeta5L). RGS9 and Gbeta5L also form a complex when coexpressed in cell culture. Our data are consistent with the recent observation that several RGS proteins, including RGS9, contain G protein gamma-subunit like domain that can mediate their association with Gbeta5 (Snow, B. E., Krumins, A. M., Brothers, G. M., Lee, S. F., Wall, M. A., Chung, S., Mangion, J., Arya, S., Gilman, A. G. & Siderovski, D. P. (1998) Proc. Natl. Acad. Sci. USA 95, 13307-13312). We report an example of such a complex whose cellular localization and function are clearly defined.
Department of Ophthalmology, Harvard Medical School, and the Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.
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Makino
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Handy
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Li
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Arshavsky
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D000939:Epitopes / Q000737:chemistry; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D046911:Macromolecular Substances; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D015293:Transducin / Q000302:isolation & purification / Q000378:metabolism*; D014714:Vertebrates; D020703:ras GTPase-Activating Proteins; D018631:ras Proteins / Q000378:metabolism
D000906:Antibodies; D000939:Epitopes; D020690:GTPase-Activating Proteins; D046911:Macromolecular Substances; D011506:Proteins; D020703:ras GTPase-Activating Proteins; D012243:Rhodopsin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D015293:Transducin; D018631:ras Proteins