2fmx
An open conformation of switch I revealed by Sar1-GDP crystal structure at low Mg(2+)An open conformation of switch I revealed by Sar1-GDP crystal structure at low Mg(2+)
Structural highlights
Function[SAR1B_CRIGR] Involved in transport from the endoplasmic reticulum to the Golgi apparatus. Activated by the guanine nucleotide exchange factor PREB. Involved in the selection of the protein cargo and the assembly of the COPII coat complex.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMg2+ 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. 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:16899220[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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