View source for 2fmx

[[Image:2fmx.jpg|left|200px]]

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{{STRUCTURE_2fmx|  PDB=2fmx  |  SCENE=  }} 

'''An open conformation of switch I revealed by Sar1-GDP crystal structure at low Mg(2+)'''


==Overview==
Mg2+ is essential for guanosine triphosphatase activity and plays key roles in guanine nucleotide binding and preserving the structural integrity of GTP-binding proteins. To understand the structural basis for Mg2+ function during the GDP/GTP exchange process, we determined the crystal structure of Delta9-Sar1-GDP at low Mg2+ concentration at 1.8A. Two Sar1-GDP molecules in the crystal form a dimer with Mg2+ presenting only in molecule B but not in molecule A. The absence of Mg2+ induces significant conformational changes in the switch I region in molecule A that shows similarities with those of Ha-Ras bound to Sos. The current structure reveals an important regulatory role for Mg2+. We suggest that guanine nucleotide exchange factor may utilize this feature to generate an open conformation for GDP/GTP exchange. Furthermore, we propose a mechanism for COPII assembly and disassembly in which dimerization of Sar1 plays an important role.

==About this Structure==
2FMX is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Cricetulus_griseus Cricetulus griseus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2FMX OCA]. 

==Reference==
An open conformation of switch I revealed by Sar1-GDP crystal structure at low Mg2+., Rao Y, Bian C, Yuan C, Li Y, Chen L, Ye X, Huang Z, Huang M, Biochem Biophys Res Commun. 2006 Sep 29;348(3):908-15. Epub 2006 Aug 1. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/16899220 16899220]
[[Category: Cricetulus griseus]]
[[Category: Single protein]]
[[Category: Bian, C.]]
[[Category: Huang, M.]]
[[Category: Li, Y.]]
[[Category: Rao, Y.]]
[[Category: Yuan, C.]]
[[Category: Cop ii assembly]]
[[Category: Crystal structure]]
[[Category: Dimerization]]
[[Category: Sar1]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May  4 04:05:04 2008''