Yang Z N, Bosron W F, Hurley T D
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202, USA.
J Mol Biol. 1997 Jan 24;265(3):330-43. doi: 10.1006/jmbi.1996.0731.
The crystal structure of the human class III chi chi alcohol dehydrogenase (ADH) in a binary complex with NAD+(gamma) was solved to 2.7 A resolution by molecular replacement with human class I beta1 beta1 ADH. chi chi ADH catalyzes the oxidation of long-chain alcohols such as omega-hydroxy fatty acids as well as S-hydroxymethyl-glutathione, a spontaneous adduct between formaldehyde and glutathione. There are two subunits per asymmetric unit in the chi chi ADH structure. Both subunits display a semi-open conformation of the catalytic domain. This conformation is half-way between the open and closed conformations described for the horse EE ADH enzyme. The semi-open conformation and key changes in elements of secondary structure provide a structural basis for the ability of chi chi ADH to bind S-hydroxymethyl-glutathione and 10-hydroxydecanoate. Direct coordination of the catalytic zinc ion by Glu68 creates a novel environment for the catalytic zinc ion in chi chi ADH. This new configuration of the catalytic zinc is similar to an intermediate for horse EE ADH proposed through theoretical computations and is consistent with the spectroscopic data of the Co(II)-substituted chi chi enzyme. The position for residue His47 in the chi chi ADH structure suggests His47 may function both as a catalytic base for proton transfer and in the binding of the adenosine phosphate of NAD(H). Modeling of substrate binding to this enzyme structure is consistent with prior mutagenesis data which showed that both Asp57 and Arg115 contribute to glutathione binding and that Arg115 contributes to the binding of omega-hydroxy fatty acids and identifies additional residues which may contribute to substrate binding.
通过以人I类β1β1乙醇脱氢酶（ADH）进行分子置换，解析了人III类奇奇乙醇脱氢酶（ADH）与NAD⁺（γ）二元复合物的晶体结构，分辨率达到2.7 Å。奇奇ADH催化长链醇的氧化，如ω-羟基脂肪酸以及S-羟甲基谷胱甘肽（甲醛与谷胱甘肽的自发加合物）。在奇奇ADH结构中，每个不对称单元有两个亚基。两个亚基均呈现催化结构域的半开放构象。这种构象处于为马EE ADH酶所描述的开放构象和封闭构象之间的中间状态。半开放构象以及二级结构元件的关键变化为奇奇ADH结合S-羟甲基谷胱甘肽和10-羟基癸酸的能力提供了结构基础。Glu68对催化锌离子的直接配位为奇奇ADH中的催化锌离子创造了一种新环境。这种催化锌的新构型类似于通过理论计算提出的马EE ADH的一种中间体，并且与Co（II）取代的奇奇酶的光谱数据一致。奇奇ADH结构中His47残基的位置表明His47可能既作为质子转移的催化碱，又参与NAD（H）磷酸腺苷的结合。底物与该酶结构结合的模型与先前的诱变数据一致，先前的数据表明Asp57和Arg115都有助于谷胱甘肽的结合，并且Arg115有助于ω-羟基脂肪酸的结合，并确定了可能有助于底物结合的其他残基。
