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| - | [[Image:1svk.gif|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_1svk| PDB=1svk | SCENE= }} | | {{STRUCTURE_1svk| PDB=1svk | SCENE= }} |
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| - | '''Structure of the K180P mutant of Gi alpha subunit bound to AlF4 and GDP'''
| + | ===Structure of the K180P mutant of Gi alpha subunit bound to AlF4 and GDP=== |
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| - | ==Overview==
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| - | Heterotrimeric G protein alpha (G alpha) subunits possess intrinsic GTPase activity that leads to functional deactivation with a rate constant of approximately 2 min(-1) at 30 degrees C. GTP hydrolysis causes conformational changes in three regions of G alpha, including Switch I and Switch II. Mutation of G202-->A in Switch II of G alpha(i1) accelerates the rates of both GTP hydrolysis and conformational change, which is measured by the loss of fluorescence from Trp-211 in Switch II. Mutation of K180-->P in Switch I increases the rate of conformational change but decreases the GTPase rate, which causes transient but substantial accumulation of a low-fluorescence G alpha(i1).GTP species. Isothermal titration calorimetric analysis of the binding of (G202A)G alpha(i1) and (K180P)G alpha(i1) to the GTPase-activating protein RGS4 indicates that the G202A mutation stabilizes the pretransition state-like conformation of G alpha(i1) that is mimicked by the complex of G alpha(i1) with GDP and magnesium fluoroaluminate, whereas the K180P mutation destabilizes this state. The crystal structures of (K180P)G alpha(i1) bound to a slowly hydrolyzable GTP analog, and the GDP.magnesium fluoroaluminate complex provide evidence that the Mg(2+) binding site is destabilized and that Switch I is torsionally restrained by the K180P mutation. The data are consistent with a catalytic mechanism for G alpha in which major conformational transitions in Switch I and Switch II are obligate events that precede the bond-breaking step in GTP hydrolysis. In (K180P)G alpha(i1), the two events are decoupled kinetically, whereas in the native protein they are concerted.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_15128951}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 15128951 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_15128951}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Gi alpha subunit]] | | [[Category: Gi alpha subunit]] |
| | [[Category: K180p mutation]] | | [[Category: K180p mutation]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 09:11:16 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 06:47:42 2008'' |
Revision as of 03:47, 28 July 2008
Template:STRUCTURE 1svk
Structure of the K180P mutant of Gi alpha subunit bound to AlF4 and GDP
Template:ABSTRACT PUBMED 15128951
About this Structure
1SVK is a Single protein structure of sequence from Rattus norvegicus. Full crystallographic information is available from OCA.
Reference
Uncoupling conformational change from GTP hydrolysis in a heterotrimeric G protein alpha-subunit., Thomas CJ, Du X, Li P, Wang Y, Ross EM, Sprang SR, Proc Natl Acad Sci U S A. 2004 May 18;101(20):7560-5. Epub 2004 May 5. PMID:15128951
Page seeded by OCA on Mon Jul 28 06:47:42 2008
