Roth Christian, Kaschabek Stefan R, Gröning Janosch A D, Handrek Thomas, Schlömann Michael, Sträter Norbert
Center for Biotechnology and Biomedicine, Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, University of Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2012 May 1;68(Pt 5):591-5. doi: 10.1107/S1744309112011888. Epub 2012 Apr 21.
Chloroaromatic compounds are often very persistent environmental pollutants. Nevertheless, numerous bacteria are able to metabolize these compounds and to utilize them as sole energy and carbon sources. Rhodococcus opacus 1CP is able to degrade several chloroaromatic compounds, some of them via a variation of the 3-chlorocatechol branch of the modified ortho-cleavage pathway. This branch in R. opacus differs from that in Proteobacteria in the inability of the chloromuconate cycloisomerase to dehalogenate. Instead, a unique enzyme designated as chloromuconolactone dehalogenase (ClcF) is recruited. ClcF dehalogenates 5-chloromuconolactone to cis-dienelactone and shows a high similarity to muconolactone isomerases (EC 5.3.3.4). However, unlike the latter enzymes, it is unable to catalyse the isomerization of muconolactone to 3-oxoadipate enollactone. In order to characterize the catalytic mechanism of this unusual dehalogenase, the enzyme was crystallized and subjected to X-ray structural analysis. Data sets to up to 1.65 Å resolution were collected from two different crystal forms using synchrotron radiation. Crystal form I (space group P2(1)) contained 40 subunits in the asymmetric unit, whereas ten subunits were present in crystal form II (space group P2(1)2(1)2(1)). The self-rotation function revealed the orientations of the molecular symmetry axes of the homodecamer of 52 symmetry.
氯代芳香族化合物通常是非常持久的环境污染物。然而，许多细菌能够代谢这些化合物，并将其用作唯一的能量和碳源。不透明红球菌1CP能够降解几种氯代芳香族化合物，其中一些是通过改良邻位裂解途径的3-氯儿茶酚分支的变体进行降解的。不透明红球菌中的这个分支与变形菌中的不同，在于氯粘康酸环异构酶无法进行脱卤反应。相反，一种名为氯粘康醇内酯脱卤酶（ClcF）的独特酶被启用。ClcF将5-氯粘康醇内酯脱卤生成顺式二烯内酯，并且与粘康醇内酯异构酶（EC 5.3.3.4）具有高度相似性。然而，与后一种酶不同的是，它无法催化粘康醇内酯异构化为3-氧代己二酸烯醇内酯。为了表征这种不寻常脱卤酶的催化机制，该酶被结晶并进行了X射线结构分析。使用同步辐射从两种不同的晶体形式收集了分辨率高达1.65 Å的数据集。晶体形式I（空间群P2(1)）在不对称单元中包含40个亚基，而晶体形式II（空间群P2(1)2(1)2(1)）中存在10个亚基。自旋转函数揭示了52对称性的同十聚体的分子对称轴的方向。
