论文部分内容阅读
Sar1 is a small GTPase involved in COPII vesicle transport. Previous studies showed that H79G mutation of Sarl can lock Sar1 in its GTP-bound active conformation, stabilize coat assembly, and prevent the disassembly of COP II vesicle coats by reducing Sec23/24 GAP- stimulated hydrolysis. We show here that the replacement of His79 by glycine induces a large conformation change in switch II and results in the lost of hydrogen bond between His79 and its associated nucleophilic water molecule that was hypothesized to reduce the GAP-stimulated hy- drolysis during the COP II assembly and disassembly. These results confirm that the switch II con- formation is important for COP II disassembly through coat-controlled GTP hydrolysis.
Sar1 is a small GTPase involved in COPII vesicle transport. Previous studies showed that H79G mutation of Sarl can lock Sar1 in its GTP-bound active conformation, stabilize coat assembly, and prevent the disassembly of COP II vesicle coats by reducing Sec 23/24 GAP- stimulated hydrolysis. We show here that the replacement of His79 by glycine induces a large conformation change in switch II and results in the lost hydrogen bond between His79 and its associated nucleophilic water molecule that was hypothesized to reduce the GAP-stimulated hy- drolysis during the COP II assembly and disassembly. These results confirm that the switch II con- formation is important for COP II disassembly through coat-controlled GTP hydrolysis.