X-ray crystal structures of transforming p21 ras mutants suggest a transition-state stabilization mechanism for GTP hydrolysis.
X-ray crystal structures of transforming p21 ras mutants suggest a transition-state stabilization mechanism for GTP hydrolysis.
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DOI：
10.1073/pnas.89.8.3649
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发表时间：
1992-04
影响因子：
11.1
通讯作者：
Gilbert G. PRIVl;Michael V. Milburn;L. Tong;Abraham M. Devos;Ziro Yamaizumiii;Susumu Nishimuraii;Sung-Hou Kim
中科院分区：
文献类型：
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作者：
Gilbert G. PRIVl;Michael V. Milburn;L. Tong;Abraham M. Devos;Ziro Yamaizumiii;Susumu Nishimuraii;Sung-Hou Kim
从人肿瘤中分离的RAS基因通常在对应于编码蛋白质（p21）的氨基酸12或61的位置处具有突变，而逆转录病毒ras编码的p21在位置12和59处均含有取代。这些突变蛋白缺乏GTP水解活性，这种活性的丧失与它们的转化潜力有关。突变蛋白质的晶体结构在此呈现为GDP结合或GTP类似物结合的复合物。基于这些结构，p21 GTdR反应的机制，提出了与所观察到的结构和生化数据是一致的。该机制的中心特征是在Gln-61侧链和GTP过渡态的五价γ-磷酸盐之间形成的特定稳定复合物。第61位上除谷氨酰胺以外的氨基酸不能稳定过渡态，而第12位上比甘氨酸大的氨基酸会干扰过渡态复合物。Thr-59破坏残基61的正常位置，从而阻止其参与过渡态复合物。
RAS genes isolated from human tumors often have mutations at positions corresponding to amino acid 12 or 61 of the encoded protein (p21), while retroviral ras-encoded p21 contains substitutions at both positions 12 and 59. These mutant proteins are deficient in their GTP hydrolysis activity, and this loss of activity is linked to their transforming potential. The crystal structures of the mutant proteins are presented here as either GDP-bound or GTP-analogue-bound complexes. Based on these structures, a mechanism for the p21 GTPase reaction is proposed that is consistent with the observed structural and biochemical data. The central feature of this mechanism is a specific stabilization complex formed between the Gln-61 side-chain and the pentavalent gamma-phosphate of the GTP transition state. Amino acids other than glutamine at position 61 cannot stabilize the transition state, and amino acids larger than glycine at position 12 would interfere with the transition-state complex. Thr-59 disrupts the normal position of residue 61, thus preventing its participation in the transition-state complex.