PDBsum entry 1as2

Signal transduction

PDB id: 1as2

Contents

Protein chain

315 a.a.

Ligands

PO4

GDP

Waters ×5

References listed in PDB file

Key reference

• Title: Structural and biochemical characterization of the gtpgammas-, Gdp.Pi-, And gdp-Bound forms of a gtpase-Deficient gly42 --≫ val mutant of gialpha1.
• Authors: A.S.Raw, D.E.Coleman, A.G.Gilman, S.R.Sprang.
• Ref.: Biochemistry, 1997, 36, 15660-15669. [DOI no: 10.1021/bi971912p]
• PubMed id: 9398294

Note In the PDB file this reference is annotated as "TO BE PUBLISHED". The citation details given above were identified by an automated search of PubMed on title and author names, giving a percentage match of 85%.

Abstract

The Gly42 --> Val mutant of Gialpha1 was characterized structurally and biochemically to elucidate two important features of Gialpha1-catalyzed GTP hydrolysis. The crystal structure of the GTPgammaS-bound G42VGialpha1 protein demonstrates that the steric bulk of Val42 pushes the Gln204 residue into a catalytically incompetent conformation, providing a rationale for the diminished GTPase activity of this mutant. The same phenomenon may also account for the diminished GTPase activity of the homologous transforming Gly42 --> Val mutation in p21(ras). Similarly, the steric bulk of the unique Ser42 residue in Gzalpha may account for the comparatively slower rate of GTP hydrolysis by this Galpha subunit. The G42VGialpha1 subunit was also characterized structurally in its GDP.Pi- and GDP-bound states, providing a unique opportunity to view three "snapshots" of GTP hydrolysis. Hydrolysis of GTP to a transient GDP.Pi-bound intermediate is associated with substantial conformational changes in the switch II segment of the protein. Eventual release of Pi results in further removal of switch I from the active site and a highly mobile switch II segment. Despite their disparate biochemical properties, the structural similarity of G42VGialpha1 to the G203AGialpha1 mutant in the GDP.Pi-bound form suggests that both mutations stabilize a conformation of the GDP. Pi-bound protein that occurs only transiently in the wild-type protein. The structures of the GDP-bound forms of the wild-type and mutant proteins are similar.