P-O bond destabilization accelerates phosphoenzyme hydrolysis of sarcoplasmic reticulum Ca2+-ATPase
P-O bond destabilization accelerates phosphoenzyme hydrolysis of sarcoplasmic reticulum Ca2+-ATPase
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DOI：
10.1074/jbc.m410867200
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发表时间：
2004-12-10
影响因子：
4.8
通讯作者：
Bezlyepkina, N
中科院分区：
文献类型：
--
作者：
Barth, A;Bezlyepkina, N
用红外光谱研究肌浆网Ca ~（2+）-ATP酶（SERCA 1a）的ADP不敏感磷酸酶（E2-P）的磷酸基团，以了解E2-P的高水解速率。通过监测自催化的同位素交换反应，在50，000个蛋白质振动的背景下选择性地观察到瞬时结合的磷酸基团的三个伸缩振动。它们分别位于1194、1137和1115 cm（-1）处。这一信息进行了评估，使用键价模型和经验相关性。与模型化合物乙酰磷酸相比，E2-磷酸正丙酯的结构和电荷分布与离解磷酸转移反应的过渡态有一定的相似性; E2-P的正丙基磷酸酯具有0.02埃短的末端P-O键和0.09埃长的桥接P-O键，其类似于弱20%，末端P-O键之间的角度较宽，并且-0.2形式电荷从磷酸基团转移到乙酰基部分。E2-P的较弱桥连P-O键导致水解速率提高10（11）~ 10（15）倍，表明P-O键的不稳定促进了磷酸酶的水解。P-O键的不稳定是由非共价相互作用从磷酸氧转移到乙酰氧引起的。我们认为Mg ~（2+）和Lys（684）在磷酸和乙酰氧之间的相对位置控制着ATP酶磷酸酶和相关磷蛋白的水解速率。
The phosphate group of the ADP-insensitive phosphoenzyme (E2-P) of sarcoplasmic reticulum Ca2+-ATPase (SERCA1a) was studied with infrared spectroscopy to understand the high hydrolysis rate of E2-P. By monitoring an autocatalyzed isotope exchange reaction, three stretching vibrations of the transiently bound phosphate group were selectively observed against a background of 50,000 protein vibrations. They were found at 1194, 1137, and 1115 cm(-1). This information was evaluated using the bond valence model and empirical correlations. Compared with the model compound acetyl phosphate, structure and charge distribution of the E2-P aspartyl phosphate resemble somewhat the transition state in a dissociative phosphate transfer reaction; the aspartyl phosphate of E2-P has 0.02 Angstrom shorter terminal P-O bonds and a 0.09 Angstrom longer bridging P-O bond that is similar to20% weaker, the angle between the terminal P-O bonds is wider, and -0.2 formal charges are shifted from the phosphate group to the aspartyl moiety. The weaker bridging P-O bond of E2-P accounts for a 10(11)-10(15)-fold hydrolysis rate enhancement, implying that P-O bond destabilization facilitates phosphoenzyme hydrolysis. P-O bond destabilization is caused by a shift of noncovalent interactions from the phosphate oxygens to the aspartyl oxygens. We suggest that the relative positioning of Mg2+ and Lys(684) between phosphate and aspartyl oxygens controls the hydrolysis rate of the ATPase phosphoenzymes and related phosphoproteins.