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题目:: Phosphatidylinositol 3,4,5-trisphosphate and Ca2+/calmodulin competitively bind to the regulators of G-protein-signalling (RGS) domain of RGS4 and reciprocally regulate its action.
作者:: Ishii(Masaru),Fujita(Satoru),Yamada(Mitsuhiko),Hosaka(Yukio),Kurachi(Yoshihisa)
状态:: 发布时间2004-12-13 , 更新时间 2014-06-08
期刊:: Biochem J
摘要:: RGS (regulators of G-protein signalling) are a diverse group of proteins, which accelerate intrinsic GTP hydrolysis on heterotrimeric G-protein a subunits. They are involved in the control of a physiological behaviour known as 'relaxation' of G-protein-gated K+ channels in cardiac myocytes. The GTPase-accelerating activity of cardiac RGS proteins, such as RGS4, is inhibited by PtdIns(3,4,5)P3 (phosphatidylinositol 3,4,5-trisphosphate) and this inhibition is cancelled by Ca2+/calmodulin (CaM) formed during membrane depolarization. G-protein-gated K+ channel activity decreases on depolarization owing to the facilitation of GTPase-activating protein activity by RGS proteins and vice versa on hyperpolarization. The molecular mechanism responsible for this reciprocal control of RGS action by PtdIns(3,4,5)P3 and Ca2+/CaM, however, has not been fully elucidated. Using lipid-protein co-sedimentation assay and surface plasmon resonance measurements, we show in the present study that the control of the GTPase-accelerating activity of the RGS4 protein is achieved through the competitive binding of PtdIns(3,4,5)P3 and Ca2+/CaM within its RGS domain. Competitive binding occurs exclusively within the RGS domain and involves a cluster of positively charged residues located on the surface opposite to the Ga interaction site. In the RGS proteins conserving these residues, the reciprocal regulation by PtdIns(3,4,5)P3 and Ca2+/CaM may be important for their physiological regulation of G-protein signalling.
语言:: eng
DOI:

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