Photosystem I(PSI)is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin(or cytochrome c6)and the reduction of ferredoxin.This catalytic reaction is realized by a transmembrane el...Photosystem I(PSI)is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin(or cytochrome c6)and the reduction of ferredoxin.This catalytic reaction is realized by a transmembrane electron transfer chain consisting of primary electron donor(a special chlorophyll(Chl)pair)and electron acceptors A_(0),A_(1),and three Fe_(4)S_(4) clusters,F_(X),F_(A),and F_(B).Here we report the PSI structure from a Chl d-dominated cyanobacterium Acaryochloris marina at 3.3Åresolution obtained by single-particle cryo-electron microscopy.The A.marina PSI exists as a trimer with three identical monomers.Surprisingly,the structure reveals a unique composition of electron transfer chain in which the primary electron acceptor A_(0) is composed of two pheophytin a rather than Chl a found in any other well-known PSI structures.A novel subunit Psa27 is observed in the A.marina PSI structure.In addition,77 Chls,13α-carotenes,two phylloquinones,three Fe-S clusters,two phosphatidyl glycerols,and one monogalactosyl-diglyceride were identified in each PSI monomer.Our results provide a structural basis for deciphering the mechanism of photosynthesis in a PSI complex with Chl d as the dominating pigments and absorbing far-red light.展开更多
基金The project was funded by the National Key R&D Program of China(2020YFA0907600,2017YFA0503700,2017YFA0504803,2018YFA0507700,2019YFA0906300)the Strategic Priority Research Program of CAS(XDA27050402,XDB17000000)+2 种基金the Chinese Academy of Sciences Key Research Program of Frontier Sciences(QYZDY-SSW-SMC003)Youth Innovation Promotion Association of CAS(2020081),CAS Interdisciplinary Innovation Team(JCTD-2020-06)the Fundamental Research Funds for the Central Universities(2018XZZX001-13).
文摘Photosystem I(PSI)is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin(or cytochrome c6)and the reduction of ferredoxin.This catalytic reaction is realized by a transmembrane electron transfer chain consisting of primary electron donor(a special chlorophyll(Chl)pair)and electron acceptors A_(0),A_(1),and three Fe_(4)S_(4) clusters,F_(X),F_(A),and F_(B).Here we report the PSI structure from a Chl d-dominated cyanobacterium Acaryochloris marina at 3.3Åresolution obtained by single-particle cryo-electron microscopy.The A.marina PSI exists as a trimer with three identical monomers.Surprisingly,the structure reveals a unique composition of electron transfer chain in which the primary electron acceptor A_(0) is composed of two pheophytin a rather than Chl a found in any other well-known PSI structures.A novel subunit Psa27 is observed in the A.marina PSI structure.In addition,77 Chls,13α-carotenes,two phylloquinones,three Fe-S clusters,two phosphatidyl glycerols,and one monogalactosyl-diglyceride were identified in each PSI monomer.Our results provide a structural basis for deciphering the mechanism of photosynthesis in a PSI complex with Chl d as the dominating pigments and absorbing far-red light.
