1gfi
|
STRUCTURES OF ACTIVE CONFORMATIONS OF GI ALPHA 1 AND THE MECHANISM OF GTP HYDROLYSIS
OverviewOverview
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 StructureAbout this Structure
1GFI is a Single protein structure of sequence from Rattus norvegicus with MG, ALF and GDP as ligands. Full crystallographic information is available from OCA.
ReferenceReference
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 Tue Nov 20 16:00:37 2007