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.
The line below this paragraph, {{ABSTRACT_PUBMED_9398294}}, adds the Publication Abstract to the page
(as it appears on PubMed at http://www.pubmed.gov), where 9398294 is the PubMed ID number.
-->
{{ABSTRACT_PUBMED_9398294}}
==About this Structure==
==About this Structure==
Line 28:
Line 32:
[[Category: Gtpase]]
[[Category: Gtpase]]
[[Category: Signal transduction]]
[[Category: Signal transduction]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 10:38:10 2008''
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 17:29:47 2008''
Revision as of 17:29, 30 June 2008
This article has been automatically seeded. Changes to this page should pertain to the PDB entry only and not to the protein or biomolecule in general.
Structural and biochemical characterization of the GTPgammaS-, GDP.Pi-, and GDP-bound forms of a GTPase-deficient Gly42 --> Val mutant of Gialpha1., Raw AS, Coleman DE, Gilman AG, Sprang SR, Biochemistry. 1997 Dec 16;36(50):15660-9. PMID:9398294
