Download MendeleyAn open conformation of switch I revealed by Sar1-GDP crystal structure at low Mg(2+)
Rao, Y., Bian, C., Yuan, C., Li, Y., Chen, L., Ye, X., Huang, Z., Huang, M.(2006) Biochem Biophys Res Commun 348: 908-915
- PubMed: 16899220
- DOI: https://doi.org/10.1016/j.bbrc.2006.07.148
- Primary Citation of Related Structures:
2FMX - 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.
Organizational Affiliation:
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yang Qiao Xi Lu, Fuzhou 350002, People's Republic of China.
