کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1939232 | 1050757 | 2006 | 8 صفحه PDF | دانلود رایگان |
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 ▵9-Sar1-GDP at low Mg2+ concentration at 1.8 Å. 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.
Journal: Biochemical and Biophysical Research Communications - Volume 348, Issue 3, 29 September 2006, Pages 908–915