3rap
From Proteopedia
(New page: 200px<br /> <applet load="3rap" size="450" color="white" frame="true" align="right" spinBox="true" caption="3rap, resolution 2.2Å" /> '''The small G protein ...) |
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| - | [[Image:3rap.gif|left|200px]]<br /> | + | [[Image:3rap.gif|left|200px]]<br /><applet load="3rap" size="350" color="white" frame="true" align="right" spinBox="true" |
| - | <applet load="3rap" size=" | + | |
caption="3rap, resolution 2.2Å" /> | caption="3rap, resolution 2.2Å" /> | ||
'''The small G protein Rap2 in a non catalytic complex with GTP'''<br /> | '''The small G protein Rap2 in a non catalytic complex with GTP'''<br /> | ||
==Overview== | ==Overview== | ||
| - | We report a novel crystal form of the small G protein Rap2A in complex | + | We report a novel crystal form of the small G protein Rap2A in complex with GTP which has no GTPase activity in the crystal. The asymmetric unit contains two complexes which show that a conserved switch I residue, Tyr 32, contributes an extra hydrogen bond to the gamma-phosphate of GTP as compared to related structures with GTP analogs. Since GTP is not hydrolyzed in the crystal, this interaction is unlikely to contribute to the intrinsic GTPase activity. The comparison of other G protein structures to the Rap2-GTP complex suggests that an equivalent interaction is likely to exist in their GTP form, whether unbound or bound to an effector. This interaction has to be released to allow the GAP-activated GTPase, and presumably the intrinsic GTPase activity as well. We also discuss the definition of the flexible regions and their hinges in the light of this structure and the expanding database of G protein structures. We propose that the switch I and switch II undergo either partial or complete disorder-to-order transitions according to their cellular status, thus defining a complex energy landscape comprising more than two conformational states. We observe in addition that the region connecting the switch I and switch II is flexible in Rap2 and other G proteins. This region may be important for protein-protein interactions and possibly behave as a conformational lever arm, as characterized for Arf. Taken together, these observations suggest that the structural mechanisms of small G proteins are significantly driven by entropy-based free energy changes. |
==About this Structure== | ==About this Structure== | ||
| - | 3RAP is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with MG and GTP as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | + | 3RAP is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=MG:'>MG</scene> and <scene name='pdbligand=GTP:'>GTP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3RAP OCA]. |
==Reference== | ==Reference== | ||
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[[Category: signaling protein]] | [[Category: signaling protein]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 19:11:07 2008'' |
Revision as of 17:11, 21 February 2008
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The small G protein Rap2 in a non catalytic complex with GTP
Overview
We report a novel crystal form of the small G protein Rap2A in complex with GTP which has no GTPase activity in the crystal. The asymmetric unit contains two complexes which show that a conserved switch I residue, Tyr 32, contributes an extra hydrogen bond to the gamma-phosphate of GTP as compared to related structures with GTP analogs. Since GTP is not hydrolyzed in the crystal, this interaction is unlikely to contribute to the intrinsic GTPase activity. The comparison of other G protein structures to the Rap2-GTP complex suggests that an equivalent interaction is likely to exist in their GTP form, whether unbound or bound to an effector. This interaction has to be released to allow the GAP-activated GTPase, and presumably the intrinsic GTPase activity as well. We also discuss the definition of the flexible regions and their hinges in the light of this structure and the expanding database of G protein structures. We propose that the switch I and switch II undergo either partial or complete disorder-to-order transitions according to their cellular status, thus defining a complex energy landscape comprising more than two conformational states. We observe in addition that the region connecting the switch I and switch II is flexible in Rap2 and other G proteins. This region may be important for protein-protein interactions and possibly behave as a conformational lever arm, as characterized for Arf. Taken together, these observations suggest that the structural mechanisms of small G proteins are significantly driven by entropy-based free energy changes.
About this Structure
3RAP is a Single protein structure of sequence from Homo sapiens with and as ligands. Full crystallographic information is available from OCA.
Reference
Structure of the small G protein Rap2 in a non-catalytic complex with GTP., Menetrey J, Cherfils J, Proteins. 1999 Nov 15;37(3):465-73. PMID:10591105
Page seeded by OCA on Thu Feb 21 19:11:07 2008
Categories: Homo sapiens | Single protein | Cherfils, J. | Menetrey, J. | GTP | MG | G protein | Gtpase | Rap2 | Ras | Signaling protein
