Crystal structures of human 108V and 108M catechol O-methyltransferase
Crystal structures of human 108V and 108M catechol O-methyltransferase
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DOI：
10.1016/j.jmb.2008.04.040
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发表时间：
2008-06-27
影响因子：
5.6
通讯作者：
Person, Vu. W.
中科院分区：
文献类型：
--
作者：
Rutherford, K.;Le Trong, I.;Person, Vu. W.
儿茶酚O-甲基转移酶（COMT）在儿茶酚胺神经递质和儿茶酚雌激素的代谢中发挥重要作用。用于治疗帕金森病的 COMT 抑制剂的开发得益于大鼠酶的晶体结构。然而，人类和大鼠蛋白质具有显着不同的底物特异性。此外，人COMT在108位含有常见的缬氨酸-甲硫氨酸多态性。甲硫氨酸蛋白的稳定性低于缬氨酸多态性，导致体内酶活性和蛋白质水平降低。在这里，我们描述了与 S-腺苷甲硫氨酸 (SAM) 和底物类似物 3,5-二硝基儿茶酚结合的人 COMT 可溶形式的 108V 和 108M 变体的晶体结构。多态性残基 108 位于 α 5-β 3 环中，埋藏在距 SAM 结合位点约 16 埃的疏水袋中。 108V和108M结构总体上非常相似[两个结构之间的C-α原子的RMSD (C-α RMSD) = 0.2埃]，并且活性位点残基是可叠加的，这与SAM稳定108M COMT的观察结果一致。然而，蛋氨酸侧链在多态性位点内堆积得更紧密，因此与残基 A22 (α 2) 和 R78 (α 4) 的相互作用比缬氨酸更紧密。较大蛋氨酸的这些相互作用导致残基 108 附近的主链结构发生 0.7 埃的位移，该位移沿着 α 1 和 α 5 向 SAM 结合位点传播。尽管人和大鼠蛋白的总体二级结构非常相似（C-α RMSD = 0.4 埃），但 SAM-（189M、191M、C95Y）和儿茶酚-（C173V、R201M、E202K）结合位点中存在几个非保守残基。人蛋白还含有三个额外的溶剂暴露半胱氨酸残基（C95、C173、C188），它们可能有助于分子间二硫键的形成和蛋白质聚集。 (C) 2008 Elsevier Ltd. 保留所有权利。
Catechol O-methyltransferase (COMT) plays important roles in the metabolism of catecholamine neurotransmitters and catechol estrogens. The development of COMT inhibitors for use in the treatment of Parkinson's disease has been aided by crystallographic structures of the rat enzyme. However, the human and rat proteins have significantly different substrate specificities. Additionally, human COMT contains a common valine-methionine polymorphism at position 108. The methionine protein is less stable than the valine polymorph, resulting in decreased enzyme activity and protein levels in vivo. Here we describe the crystal structures of the 108V and 108M variants of the soluble form of human COMT bound with S-adenosylmethionine (SAM) and a substrate analog, 3,5-dinitrocatechol. The polymorphic residue 108 is located in the alpha 5-beta 3 loop, buried in a hydrophobic pocket similar to 16 angstrom from the SAM-binding site. The 108V and 108M structures are very similar overall [RMSD of C-alpha atoms between two structures (C-alpha RMSD) = 0.2 angstrom], and the active-site residues are superposable, in accord with the observation that SAM stabilizes 108M COMT. However, the methionine side chain is packed more tightly within the polymorphic site and, consequently, interacts more closely with residues A22 (alpha 2) and R78 (alpha 4) than does valine. These interactions of the larger methionine result in a 0.7-angstrom displacement in the backbone structure near residue 108, which propagates along alpha 1 and alpha 5 toward the SAM-binding site. Although the overall secondary structures of the human and rat proteins are very similar (C-alpha RMSD=0.4 angstrom), several nonconserved residues are present in the SAM-(189M, 191M, C95Y) and catechol- (C173V, R201M, E202K) binding sites. The human protein also contains three additional solvent-exposed cysteine residues (C95, C173, C188) that may contribute to intermolecular disulfide bond formation and protein aggregation. (C) 2008 Elsevier Ltd. All rights reserved.