Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Japan Biological Informatics Consortium (JBiC), Aomi, Koto-ku, Tokyo 135-0064, Japan.
Sci Adv. 2019 Mar 13;5(3):eaav8945. doi: 10.1126/sciadv.aav8945. eCollection 2019 Mar.
Ras-related C3 botulinum toxin substrate 1 (Rac1) plays critical roles in the maintenance of cell morphology by cycling between inactive guanosine diphosphate (GDP)-bound and active guanosine triphosphate (GTP)-bound states. Rac1 P29S mutant is known to strongly promote oncogenesis by facilitating its intrinsic GDP dissociation and thereby increasing the level of the GTP-bound state. Here, we used solution nuclear magnetic resonance spectroscopy to investigate the activation mechanism of the oncogenic P29S mutant. We demonstrate that the conformational landscape is markedly altered in the mutant, and the preexisting equilibrium is shifted toward the conformation with reduced affinity for Mg a cofactor that is critical for maintaining stable GDP binding. Our results suggest that the alternation of the preexisting conformational equilibrium of proteins is one of the fundamental mechanisms underlying their oncogenic activities.
Ras 相关的 C3 肉毒梭菌毒素底物 1（Rac1）通过在非活性鸟苷二磷酸（GDP）结合和活性鸟苷三磷酸（GTP）结合状态之间循环，在维持细胞形态中发挥关键作用。已知 Rac1 P29S 突变体通过促进其内在的 GDP 解离并从而增加 GTP 结合状态的水平，强烈促进致癌作用。在这里，我们使用溶液核磁共振波谱法来研究致癌 P29S 突变体的激活机制。我们证明突变体的构象景观发生了明显改变，并且预先存在的平衡向与降低的对 Mg2+辅助因子亲和力的构象转移，该辅助因子对于维持稳定的 GDP 结合至关重要。我们的结果表明，蛋白质预先存在的构象平衡的改变是其致癌活性的基础机制之一。
