Lancaster C R, Gross R, Simon J
Max-Planck-Institut für Biophysik, Abteilung Molekulare Membranbiologie, Frankfurt am Main, Germany.
Eur J Biochem. 2001 Mar;268(6):1820-7.
Quinol:fumarate reductase (QFR) is a membrane protein complex that couples the reduction of fumarate to succinate to the oxidation of quinol to quinone. Previously, the crystal structure of QFR from Wolinella succinogenes was determined based on two different crystal forms, and the site of fumarate binding in the flavoprotein subunit A of the enzyme was located between the FAD-binding domain and the capping domain [Lancaster, C.R.D., Kröger, A., Auer, M., & Michel, H. (1999) Nature 402, 377--385]. Here we describe the structure of W. succinogenes QFR based on a third crystal form and refined at 3.1 A resolution. Compared with the previous crystal forms, the capping domain is rotated in this structure by approximately 14 degrees relative to the FAD-binding domain. As a consequence, the topology of the dicarboxylate binding site is much more similar to those of membrane-bound and soluble fumarate reductase enzymes from other organisms than to that found in the previous crystal forms of W. succinogenes QFR. This and the effects of the replacement of Arg A301 by Glu or Lys by site-directed mutagenesis strongly support a common mechanism for fumarate reduction in this superfamily of enzymes.
延胡索酸还原酶（QFR）是一种膜蛋白复合物，它将延胡索酸还原为琥珀酸与喹啉氧化为醌的过程偶联起来。此前，基于两种不同的晶体形式确定了产琥珀酸沃林氏菌中QFR的晶体结构，并且该酶黄素蛋白亚基A中延胡索酸的结合位点位于FAD结合结构域和封端结构域之间[兰开斯特，C.R.D.，克罗格，A.，奥尔，M.，&米歇尔，H.（1999年）《自然》402，377 - 385]。在此，我们描述了基于第三种晶体形式且分辨率为3.1埃的产琥珀酸沃林氏菌QFR的结构。与之前的晶体形式相比，在这种结构中封端结构域相对于FAD结合结构域旋转了约14度。因此，二羧酸盐结合位点的拓扑结构与来自其他生物体的膜结合和可溶性延胡索酸还原酶的拓扑结构更为相似，而与产琥珀酸沃林氏菌QFR之前晶体形式中的拓扑结构不同。这一点以及通过定点诱变将精氨酸A301替换为谷氨酸或赖氨酸的效果有力地支持了该酶超家族中延胡索酸还原的共同机制。
