2ije
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(New page: 200px<br /><applet load="2ije" size="450" color="white" frame="true" align="right" spinBox="true" caption="2ije, resolution 2.2Å" /> '''Crystal Structure of ...)
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Revision as of 10:13, 21 November 2007
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Crystal Structure of the Cdc25 domain of RasGRF1
Overview
The Ras-specific guanine nucleotide-exchange factors Son of sevenless, (Sos) and Ras guanine nucleotide-releasing factor 1 (RasGRF1) transduce, extracellular stimuli into Ras activation by catalyzing the exchange of, Ras-bound GDP for GTP. A truncated form of RasGRF1 containing only the, core catalytic Cdc25 domain is sufficient for stimulating Ras nucleotide, exchange, whereas the isolated Cdc25 domain of Sos is inactive. At a site, distal to the catalytic site, nucleotide-bound Ras binds to Sos, making, contacts with the Cdc25 domain and with a Ras exchanger motif (Rem), domain. This allosteric Ras binding stimulates nucleotide exchange by Sos, but the mechanism by which this stimulation occurs has not been defined., We present a crystal structure of the Rem and Cdc25 domains of Sos, determined at 2.0-A resolution in the absence of Ras. Differences between, this structure and that of Sos bound to two Ras molecules show that, allosteric activation of Sos by Ras occurs through a rotation of the Rem, domain that is coupled to a rotation of a helical hairpin at the Sos, catalytic site. This motion relieves steric occlusion of the catalytic, site, allowing substrate Ras binding and nucleotide exchange. A structure, of the isolated RasGRF1 Cdc25 domain determined at 2.2-A resolution, combined with computational analyses, suggests that the Cdc25 domain of, RasGRF1 is able to maintain an active conformation in isolation because, the helical hairpin has strengthened interactions with the Cdc25 domain, core. These results indicate that RasGRF1 lacks the allosteric activation, switch that is crucial for Sos activity.
About this Structure
2IJE is a Single protein structure of sequence from Mus musculus with GOL as ligand. Full crystallographic information is available from OCA.
Reference
A Ras-induced conformational switch in the Ras activator Son of sevenless., Freedman TS, Sondermann H, Friedland GD, Kortemme T, Bar-Sagi D, Marqusee S, Kuriyan J, Proc Natl Acad Sci U S A. 2006 Nov 7;103(45):16692-7. Epub 2006 Oct 30. PMID:17075039
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