Hydrolysis of Guanosine Triphosphate (GTP) by the Ras路GAP Protein Complex: Reaction Mechanism and Kinetic Scheme

详细信息    查看全文

• 作者：Maria G. Khrenova ; Bella L. Grigorenko ; Anatoly B. Kolomeisky ; Alexander V. Nemukhin
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：October 8, 2015
• 年：2015
• 卷：119
• 期：40
• 页码：12838-12845
• 全文大小：456K
• ISSN：1520-5207

文摘

Molecular mechanisms of the hydrolysis of guanosine triphosphate (GTP) to guanosine diphosphate (GDP) and inorganic phosphate (Pi) by the Ras路GAP protein complex are fully investigated by using modern modeling tools. The previously hypothesized stages of the cleavage of the phosphorus鈥搊xygen bond in GTP and the formation of the imide form of catalytic Gln61 from Ras upon creation of Pi are confirmed by using the higher-level quantum-based calculations. The steps of the enzyme regeneration are modeled for the first time, providing a comprehensive description of the catalytic cycle. It is found that for the reaction Ras路GAP路GTP路H₂O 鈫?Ras路GAP路GDP路Pi, the highest barriers correspond to the process of regeneration of the active site but not to the process of substrate cleavage. The specific shape of the energy profile is responsible for an interesting kinetic mechanism of the GTP hydrolysis. The analysis of the process using the first-passage approach and consideration of kinetic equations suggest that the overall reaction rate is a result of the balance between relatively fast transitions and low probability of states from which these transitions are taking place. Our theoretical predictions are in excellent agreement with available experimental observations on GTP hydrolysis rates.