2fmx

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spinqualitylabelsall models 2fmx, resolution 1.82Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

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 Cricetulus griseus with SO4, MG and GDP as ligands. Full crystallographic information is available from 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:16899220

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