Falcioni Fabio, Molt Robert W, Jin Yi, Waltho Jonathan P, Hay Sam, Richards Nigel G J, Blackburn G Michael
Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K.
Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7DN, U.K.
ACS Catal. 2024 Apr 16;14(9):6650-6658. doi: 10.1021/acscatal.4c00380. eCollection 2024 May 3.
Arginine phosphorylation plays numerous roles throughout biology. Arginine kinase (AK) catalyzes the delivery of an anionic phosphoryl group (PO) from ATP to a planar, trigonal nitrogen in a guanidinium cation. Density functional theory (DFT) calculations have yielded a model of the transition state (TS) for the AK-catalyzed reaction. They reveal a network of over 50 hydrogen bonds that delivers unprecedented pyramidalization and out-of-plane polarization of the arginine guanidinium nitrogen (Nη2) and aligns the electron density on Nη2 with the scissile P-O bond, leading to in-line phosphoryl transfer via an associative mechanism. In the reverse reaction, the hydrogen-bonding network enforces the conformational distortion of a bound phosphoarginine substrate to increase the basicity of Nη2. This enables Nη2 protonation, which triggers PO migration to generate ATP. This polarization-pyramidalization of nitrogen in the arginine side chain is likely a general phenomenon that is exploited by many classes of enzymes mediating the post-translational modification of arginine.
精氨酸磷酸化在整个生物学过程中发挥着多种作用。精氨酸激酶（AK）催化将阴离子磷酸基团（PO）从ATP转移至胍阳离子中的平面三角氮原子上。密度泛函理论（DFT）计算得出了AK催化反应的过渡态（TS）模型。这些计算结果揭示了一个由50多个氢键构成的网络，该网络使精氨酸胍氮原子（Nη2）产生了前所未有的锥体化和平面外极化，并使Nη2上的电子密度与可断裂的P - O键对齐，从而通过缔合机制实现共线磷酸基转移。在逆反应中，氢键网络促使结合的磷酸精氨酸底物发生构象扭曲，以增加Nη2的碱性。这使得Nη2质子化，进而引发PO迁移以生成ATP。精氨酸侧链中氮原子的这种极化 - 锥体化可能是一种普遍现象，被许多介导精氨酸翻译后修饰的酶所利用。
