Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan.
Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, 30043, Taiwan.
Sci Rep. 2018 Oct 8;8(1):14935. doi: 10.1038/s41598-018-33193-5.
The membrane-embedded quinol:fumarate reductase (QFR) in anaerobic bacteria catalyzes the reduction of fumarate to succinate by quinol in the anaerobic respiratory chain. The electron/proton-transfer pathways in QFRs remain controversial. Here we report the crystal structure of QFR from the anaerobic sulphate-reducing bacterium Desulfovibrio gigas (D. gigas) at 3.6 Å resolution. The structure of the D. gigas QFR is a homo-dimer, each protomer comprising two hydrophilic subunits, A and B, and one transmembrane subunit C, together with six redox cofactors including two b-hemes. One menaquinone molecule is bound near heme b in the hydrophobic subunit C. This location of the menaquinone-binding site differs from the menaquinol-binding cavity proposed previously for QFR from Wolinella succinogenes. The observed bound menaquinone might serve as an additional redox cofactor to mediate the proton-coupled electron transport across the membrane. Armed with these structural insights, we propose electron/proton-transfer pathways in the quinol reduction of fumarate to succinate in the D. gigas QFR.
延胡索酸还原酶（QFR）在厌氧菌中催化厌氧呼吸链中醌将延胡索酸还原为琥珀酸。QFR 中的电子/质子转移途径仍存在争议。在这里，我们报告了来自厌氧硫酸盐还原菌脱硫弧菌（D. gigas）的 QFR 的晶体结构，分辨率为 3.6Å。D. gigas QFR 的结构是同源二聚体，每个单体由两个亲水亚基 A 和 B 以及一个跨膜亚基 C 组成，共包含六个氧化还原辅因子，包括两个 b-血红素。一个menaquinone 分子结合在疏水亚基 C 中的血红素 b 附近。该menaquinone 结合位点的位置与先前报道的来自伍氏脱硫弧菌的 QFR 的menaquinol 结合腔不同。观察到的结合的menaquinone 可能作为额外的氧化还原辅因子，介导质子偶联的电子穿过膜的传输。有了这些结构上的见解，我们提出了 D. gigas QFR 中延胡索酸还原为琥珀酸的醌还原中的电子/质子转移途径。
