Rho‐GTPases proteins function as molecular switches alternating from an active to an inactive state upon Guanosine triphosphate (GTP) binding and hydrolysis to Guanosine diphosphate (GDP). Among them, Rac subfamily regulates cell dynamics, being overexpressed in distinct cancer types. Notably, these proteins are object of frequent cancer‐associated mutations at Pro29 (P29S, P29L, and P29Q). To assess the impact of these mutations on Rac1 structure and function, we performed extensive all‐atom molecular dynamics simulations on wild‐type (wt) and oncogenic isoforms of this protein in GDP‐ and GTP‐bound states. Our results unprecedentedly elucidate that P29Q/S‐induced structural and dynamical perturbations of Rac1 core domain weaken the binding of the catalytic site Mg2+ ion, and reduce the GDP residence time within protein, enhancing the GDP/GTP exchange rate and Rac1 activity. This broadens our knowledge of the role of cancer‐associated mutations on small GTPases mechanism supplying valuable information for future drug discovery efforts targeting specific Rac1 isoforms.

中文翻译：

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评估 Rac1 小 Rho GTP 酶快速循环癌症相关突变的机制

Rho-GTP 酶蛋白作为分子开关，在三磷酸鸟苷 (GTP) 结合并水解为二磷酸鸟苷 (GDP) 时从活性状态切换到非活性状态。其中，Rac 亚家族调节细胞动力学，在不同的癌症类型中过度表达。值得注意的是，这些蛋白质是 Pro29（P29S、P29L 和 P29Q）频繁发生癌症相关突变的对象。为了评估这些突变对 Rac1 结构和功能的影响，我们对该蛋白在 GDP 和 GTP 结合状态下的野生型 (wt) 和致癌异构体进行了广泛的全原子分子动力学模拟。我们的结果前所未有地阐明了 P29Q/S 诱导的 Rac1 核心结构域的结构和动力学扰动削弱了催化位点 Mg 的结合2+离子，并减少 GDP 在蛋白质内的停留时间，提高 GDP/GTP 交换率和 Rac1 活性。这拓宽了我们对小 GTP 酶机制中癌症相关突变作用的认识，为未来针对特定 Rac1 亚型的药物发现工作提供了有价值的信息。