RAS proteins are commonly mutated in cancerous tumors, but germline RAS mutations are also found in RASopathy syndromes such as Noonan syndrome (NS) and cardiofaciocutaneous (CFC) syndrome. Activating RAS mutations can be subclassified based on their activating mechanisms. Understanding the structural basis for these mechanisms may provide clues for how to manage associated health conditions. We determined high‐resolution X‐ray structures of the RASopathy mutant KRAS^P34R seen in NS and CFCS. GTP and GDP‐bound KRAS^P34R crystallized in multiple forms, with each lattice consisting of multiple protein conformations. In all GTP‐bound conformations, the switch regions are not compatible with GAP binding, suggesting a structural mechanism for the GAP insensitivity of this RAS mutant. However, GTP‐bound conformations are compatible with intrinsic nucleotide hydrolysis, including one that places R34 in a position analogous to the GAP arginine finger or intrinsic arginine finger found in heterotrimeric G proteins, which may support intrinsic GTP hydrolysis. We also note that the affinity between KRAS^P34R and RAF‐RBD is decreased, suggesting another possible mechanism for dampening of RAS signaling. These results may provide a foothold for development of new mutation‐specific strategies to address KRAS^P34R‐driven diseases.

中文翻译：

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GTP 水解由 RAS 病相关 KRASP34R 中的 Arg34 调节。

RAS 蛋白通常在癌性肿瘤中发生突变，但种系 RAS 突变也见于 RAS 病综合征，如努南综合征 (NS) 和心面皮肤综合征 (CFC)。激活 RAS 突变可以根据其激活机制进行细分。了解这些机制的结构基础可能为如何管理相关健康状况提供线索。^{我们确定了 NS 和 CFCS 中出现的 RASopathy 突变体 KRAS P34R}的高分辨率 X 射线结构。GTP 和 GDP 结合的 KRAS ^P34R以多种形式结晶，每个晶格由多种蛋白质构象组成。在所有 GTP 结合构象中，开关区域与 GAP 结合不兼容，这表明该 RAS 突变体的 GAP 不敏感的结构机制。然而，GTP 结合构象与内在核苷酸水解相容，包括将 R34 置于类似于异三聚体 G 蛋白中发现的 GAP 精氨酸指或内在精氨酸指的位置，这可能支持内在 GTP 水解。^{我们还注意到 KRAS P34R}和 RAF-RBD之间的亲和力降低，这表明抑制 RAS 信号传导的另一种可能机制。^{这些结果可能为开发新的突变特异性策略来解决 KRAS P34R}驱动的疾病提供立足点。