Jormakka Mika, Yokoyama Ken, Yano Takahiro, Tamakoshi Masatada, Akimoto Satoru, Shimamura Tatsuro, Curmi Paul, Iwata So
Department of Biophysics, University of New South Wales, Barker Street, Sydney, New South Wales 2052, Australia.
Nat Struct Mol Biol. 2008 Jul;15(7):730-7. doi: 10.1038/nsmb.1434. Epub 2008 Jun 8.
Bacterial polysulfide reductase (PsrABC) is an integral membrane protein complex responsible for quinone-coupled reduction of polysulfide, a process important in extreme environments such as deep-sea vents and hot springs. We determined the structure of polysulfide reductase from Thermus thermophilus at 2.4-A resolution, revealing how the PsrA subunit recognizes and reduces its unique polyanionic substrate. The integral membrane subunit PsrC was characterized using the natural substrate menaquinone-7 and inhibitors, providing a comprehensive representation of a quinone binding site and revealing the presence of a water-filled cavity connecting the quinone binding site on the periplasmic side to the cytoplasm. These results suggest that polysulfide reductase could be a key energy-conserving enzyme of the T. thermophilus respiratory chain, using polysulfide as the terminal electron acceptor and pumping protons across the membrane via a previously unknown mechanism.
细菌多硫化物还原酶（PsrABC）是一种整合膜蛋白复合物，负责醌偶联的多硫化物还原，这一过程在深海热液喷口和温泉等极端环境中很重要。我们以2.4埃的分辨率确定了嗜热栖热菌多硫化物还原酶的结构，揭示了PsrA亚基如何识别并还原其独特的多阴离子底物。使用天然底物甲基萘醌-7和抑制剂对整合膜亚基PsrC进行了表征，全面展示了醌结合位点，并揭示了在周质侧连接醌结合位点与细胞质的充满水的腔的存在。这些结果表明，多硫化物还原酶可能是嗜热栖热菌呼吸链的关键节能酶，以多硫化物作为末端电子受体，并通过一种前所未知的机制将质子泵过膜。
