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| [[Image:1gil.jpg|left|200px]] | | {{Seed}} |
| | [[Image:1gil.png|left|200px]] |
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| {{STRUCTURE_1gil| PDB=1gil | SCENE= }} | | {{STRUCTURE_1gil| PDB=1gil | SCENE= }} |
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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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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_8073283}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 8073283 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_8073283}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Sprang, S R.]] | | [[Category: Sprang, S R.]] |
| [[Category: Gtp-binding protein]] | | [[Category: Gtp-binding protein]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 17:37:10 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 05:21:05 2008'' |