2FMX
An open conformation of switch I revealed by Sar1-GDP crystal structure at low Mg(2+)
Summary for 2FMX
| Entry DOI | 10.2210/pdb2fmx/pdb |
| Related | 1F6B 2FA9 |
| Descriptor | GTP-binding protein SAR1b, SULFATE ION, GUANOSINE-5'-DIPHOSPHATE, ... (5 entities in total) |
| Functional Keywords | sar1, cop ii assembly, dimerization, protein transport |
| Biological source | Cricetulus griseus (Chinese hamster) |
| Cellular location | Endoplasmic reticulum membrane; Peripheral membrane protein: Q9QVY3 |
| Total number of polymer chains | 2 |
| Total formula weight | 45225.50 |
| Authors | |
| Primary citation | Rao, Y.,Bian, C.,Yuan, C.,Li, Y.,Chen, L.,Ye, X.,Huang, Z.,Huang, M. An open conformation of switch I revealed by Sar1-GDP crystal structure at low Mg(2+) Biochem.Biophys.Res.Commun., 348:908-915, 2006 Cited by PubMed Abstract: 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. PubMed: 16899220DOI: 10.1016/j.bbrc.2006.07.148 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.82 Å) |
Structure validation
Download full validation report
