Publication Date:
1994-09-02
Description:
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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Coleman, D E -- Berghuis, A M -- Lee, E -- Linder, M E -- Gilman, A G -- Sprang, S R -- DK 46371/DK/NIDDK NIH HHS/ -- GM34497/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 2;265(5177):1405-12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Dallas, TX.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8073283" target="_blank"〉PubMed〈/a〉
Keywords:
Aluminum Compounds/metabolism
;
Arginine/chemistry
;
Binding Sites
;
Catalysis
;
Computer Graphics
;
Crystallography, X-Ray
;
Fluorides/metabolism
;
GTP-Binding Proteins/*chemistry/metabolism
;
Glutamine/chemistry
;
Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
;
Guanosine Diphosphate/metabolism
;
Guanosine Triphosphate/*metabolism
;
Helix-Loop-Helix Motifs
;
Hydrogen Bonding
;
Hydrolysis
;
Models, Molecular
;
*Protein Conformation
;
Protein Structure, Secondary
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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