1gil
From Proteopedia
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'''STRUCTURE OF ACTIVE CONFORMATIONS OF GIA1 AND THE MECHANISM OF GTP HYDROLYSIS''' | '''STRUCTURE OF ACTIVE CONFORMATIONS OF GIA1 AND THE MECHANISM OF GTP HYDROLYSIS''' | ||
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[[Category: Coleman, D E.]] | [[Category: Coleman, D E.]] | ||
[[Category: Sprang, S R.]] | [[Category: Sprang, S R.]] | ||
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Revision as of 14:37, 2 May 2008
STRUCTURE OF ACTIVE CONFORMATIONS OF GIA1 AND THE MECHANISM OF GTP HYDROLYSIS
Overview
Mechanisms of guanosine triphosphate (GTP) hydrolysis by members of the G protein alpha subunit-p21ras superfamily of guanosine triphosphatases have been studied extensively but have not been well understood. High-resolution x-ray structures of the GTP gamma S and GDP.AlF4- complexes formed by the G protein Gi alpha 1 demonstrate specific roles in transition-state stabilization for two highly conserved residues. Glutamine204 (Gln61 in p21ras) stabilizes and orients the hydrolytic water in the trigonal-bipyramidal transition state. Arginine 178 stabilizes the negative charge at the equatorial oxygen atoms of the pentacoordinate phosphate intermediate. Conserved only in the G alpha family, this residue may account for the higher hydrolytic rate of G alpha proteins relative to those of the p21ras family members. The fold of Gi alpha 1 differs from that of the homologous Gt alpha subunit in the conformation of a helix-loop sequence located in the alpha-helical domain that is characteristic of these proteins; this site may participate in effector binding. The amino-terminal 33 residues are disordered in GTP gamma S-Gi alpha 1, suggesting a mechanism that may promote release of the beta gamma subunit complex when the alpha subunit is activated by GTP.
About this Structure
1GIL is a Single protein structure of sequence from Rattus norvegicus. Full crystallographic information is available from OCA.
Reference
Structures of active conformations of Gi alpha 1 and the mechanism of GTP hydrolysis., Coleman DE, Berghuis AM, Lee E, Linder ME, Gilman AG, Sprang SR, Science. 1994 Sep 2;265(5177):1405-12. PMID:8073283 Page seeded by OCA on Fri May 2 17:37:10 2008
