Structural insight into the rearrangement of the switch I region in GTP-bound G12A K-Ras.
K-Ras, a molecular switch that regulates cell growth, apoptosis and metabolism, is activated when it undergoes a conformation change upon binding GTP and is deactivated following the hydrolysis of GTP to GDP. Hydrolysis of GTP in water is accelerated by coordination to K-Ras, where GTP adopts a high-energy conformation approaching the transition state. The G12A mutation reduces intrinsic K-Ras GTP hydrolysis by an unexplained mechanism. Here, crystal structures of G12A K-Ras in complex with GDP, GTP, GTPγS and GppNHp, and of Q61A K-Ras in complex with GDP, are reported. In the G12A K-Ras-GTP complex, the switch I region undergoes a significant reorganization such that the Tyr32 side chain points towards the GTP-binding pocket and forms a hydrogen bond to the GTP γ-phosphate, effectively stabilizing GTP in its precatalytic state, increasing the activation energy required to reach the transition state and contributing to the reduced intrinsic GTPase activity of G12A K-Ras mutants.
['Xu|Shenyuan|S|0000-0002-9903-1944', 'Long|Brian N|BN|', 'Boris|Gabriel H|GH|', 'Chen|Anqi|A|', 'Ni|Shuisong|S|', 'Kennedy|Michael A|MA|']
D001665:Binding Sites D018360:Crystallography, X-Ray D016244:Guanosine 5'-O-(3-Thiotriphosphate) D006153:Guanosine Diphosphate D006160:Guanosine Triphosphate D006801:Humans D006860:Hydrogen Bonding D006868:Hydrolysis D008958:Models, Molecular D009154:Mutation D011487:Protein Conformation D016283:Proto-Oncogene Proteins p21(ras)
G12A K-Ras K-Ras apoptosis GTP hydrolysis Q61A K-Ras precatalytic state cancer cell regulation cell growth regulation