1BH2

A326S MUTANT OF AN INHIBITORY ALPHA SUBUNIT

1BH2 の概要

• エントリーDOI: 10.2210/pdb1bh2/pdb
• 分子名称: GUANINE NUCLEOTIDE-BINDING PROTEIN, MAGNESIUM ION, 5'-GUANOSINE-DIPHOSPHATE-MONOTHIOPHOSPHATE, ... (4 entities in total)
• 機能のキーワード: signal transduction protein
• 由来する生物種: Rattus norvegicus (Norway rat)
• 細胞内の位置: Nucleus: P10824
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 36702.72

構造登録者

Mixon, M.B.,Posner, B.A.,Wall, M.A.,Gilman, A.G.,Sprang, S.R. (登録日: 1998-06-12, 公開日: 1998-11-04, 最終更新日: 2024-05-22)

主引用文献

Posner, B.A.,Mixon, M.B.,Wall, M.A.,Sprang, S.R.,Gilman, A.G.
The A326S mutant of Gialpha1 as an approximation of the receptor-bound state.
J.Biol.Chem., 273:21752-21758, 1998

PubMed Abstract: Agonist-bound heptahelical receptors activate heterotrimeric G proteins by catalyzing exchange of GDP for GTP on their alpha subunits. In search of an approximation of the receptor-alpha subunit complex, we have considered the properties of A326S Gialpha1, a mutation discovered originally in Gsalpha (Iiri, T., Herzmark, P., Nakamoto, J. M., Van Dop, C., and Bourne, H. R. (1994) Nature 371, 164-168) that mimics the effect of receptor on nucleotide exchange. The mutation accelerates dissociation of GDP from the alphai1beta1gamma2 heterotrimer by 250-fold. Nevertheless, affinity of mutant Gialpha1 for GTPgammaS is high in the presence of Mg2+, and the mutation has no effect on the intrinsic GTPase activity of the alpha subunit. The mutation also uncouples two activities of betagamma: stabilization of the GDP-bound alpha subunit (which is retained) and retardation of GDP dissociation from the heterotrimer (which is lost). For wild-type and mutant Gialpha1, beta gamma prevents irreversible inactivation of the alpha subunit at 30 degreesC. However, the mutation accelerates irreversible inactivation of alpha at 37 degreesC despite the presence of beta gamma. Structurally, the mutation weakens affinity for GTPgammaS by steric crowding: a 2-fold increase in the number of close contacts between the protein and the purine ring of the nucleotide. By contrast, we observe no differences in structure at the GDP binding site between wild-type heterotrimers and those containing A326S Gialpha1. However, the GDP binding site is only partially occupied in crystals of G protein heterotrimers containing A326S Gialpha1. In contrast to original speculations about the structural correlates of receptor-catalyzed nucleotide exchange, rapid dissociation of GDP can be observed in the absence of substantial structural alteration of a Galpha subunit in the GDP-bound state.

PubMed: 9705312
DOI: 10.1074/jbc.273.34.21752

実験手法

X-RAY DIFFRACTION (2.1 Å)