A cytochrome c551 mediates the cyclic electron transport chain of the anoxygenic phototrophic bacterium Roseiflexus castenholzii  

作　　者：Lu Yu Zhenzhen Min Menghua Liu Yueyong Xin Aokun Liu Jian Kuang Wenping Wu Jingyi Wu Huimin He Jiyu Xin Robert EBlankenship Changlin Tian Xiaoling Xu 

机构地区：[1]Department of Biochemistry and Molecular Biology,School of Basic Medical Sciences and Affiliated Hospital,Key Laboratory of Aging and Cancer Biology of Zhejiang Province,Hangzhou Normal University,Hangzhou 311121,China [2]High Magnetic Field Laboratory,Chinese Academy of Sciences,Hefei 230031,China [3]Photosynthesis Research Center,College of Life and Environmental Sciences,Hangzhou Normal University,Hangzhou 311121,China [4]The First Affiliated Hospital of USTC,Division of Life Sciences and Medicine,Center for Bioanalytical Chemistry,Hefei National Laboratory of Physical Science at Microscale,University of Science and Technology of China,Hefei 230026,China [5]Departments of Biology and Chemistry,Washington University in St.Louis,St.Louis,MO 63130,USA

出　　处：《Plant Communications》2024年第2期79-93,共15页植物通讯（英文）

基　　金：supported by grants from the National Natural Science Foundation of China (32171227,31870740,and 31570738 to X.X.,21825703 and 21927814 to C.T.);the National Key Research and Development Project of China (2019YFA0405600 and 2019YFA0706900 to C.T.);the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB37040000)to C.T.,;the Youth Innovation Promotion Association CAS (2022455)to L.Y.,;the Zhejiang Provincial Natural Science Foundation of China under grant LR22C020002 to X.X.

摘　　要：Roseiflexus castenholzii is a gram-negativefilamentous phototrophic bacterium that carries out anoxygenic photosynthesis through a cyclic electron transport chain(ETC).The ETC is composed of a reaction center(RC)–light-harvesting(LH)complex(rcRC–LH);an alternative complex III(rcACIII),which functionally re-places the cytochrome bc1/b6f complex;and the periplasmic electron acceptor auracyanin(rcAc).Although compositionally and structurally different from the bc1/b6f complex,rcACIII plays similar essential roles in oxidizing menaquinol and transferring electrons to the rcAc.However,rcACIII-mediated electron transfer(which includes both an intraprotein route and a downstream route)has not been clearly elucidated,nor have the details of cyclic ETC.Here,we identify a previously unknown monoheme cytochrome c(cyt c551)as a novel periplasmic electron acceptor of rcACIII.It reduces the light-excited rcRC–LH to complete a cyclic ETC.We also reveal the molecular mechanisms involved in the ETC using electron paramagnetic resonance(EPR),spectroelectrochemistry,and enzymatic and structural analyses.Wefind that electrons released from rcACIII-oxidized menaquinol are transferred to two alternative periplasmic electron acceptors(rcAc and cyt c551),which eventually reduce the rcRC to form the complete cyclic ETC.This work serves as a foundation for further studies of ACIII-mediated electron transfer in anoxygenic photosynthesis and broadens our under-standing of the diversity and molecular evolution of prokaryotic ETCs.

关 键 词：cytochrome c menaquinol oxidoreductase electron transport chain electron paramagnetic reso-nance light-harvesting complex 

分 类 号：Q94[生物学—植物学]