title: Structural and biochemical characterization of MCAT from photosynthetic microorganism Synechocystis sp. PCC 6803 reveal its stepwise catalytic mechanism.
abstract: Malonyl-coenzyme A: acyl-carrier protein transacylase (MCAT) catalyzes the transfer of malonyl group from malonyl-CoA to the holo-acyl carrier protein (Holo-ACP), yielding malonyl-ACP. The overall reaction has been extensively studied in heterotrophic microorganisms, while its mechanism in photosynthetic autotrophs as well as the stepwise reaction information remains unclear. Here the 2.42 Å crystal structure of MCAT from photosynthetic microorganism Synechocystis sp. PCC 6803 is presented. It demonstrates that Arg113, Ser88 and His188 constitute catalytic triad. The second step involved ACP-MCAT-malonyl intermediate is speed-limited instead of the malonyl-CoA-MCAT intermediate in the first step. Therefore His87, Arg113 and Ser88 render different contributions for the two intermediates. Additionally, S88T mutant initializes the reaction by H87 deprotonating S88T which is different from the wild type.
authors.affiliation: Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Yinghui
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Yanbin
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China; University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Yayue
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Dalian Polytechnic University, Dalian 116034, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.affiliation: Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
authors.forename: Xupeng
authors.initials: X
authors.lastname: Cao
authors.affiliation: Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China. Electronic address: xuesong@dicp.ac.cn.
authors.forename: Song
authors.initials: S
authors.lastname: Xue
mesh_terms: D051080:Acyl-Carrier Protein S-Malonyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D020134:Catalytic Domain; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D051080:Acyl-Carrier Protein S-Malonyltransferase
keywords: Intermediate; MCAT; Structure; Synechocystis sp. PCC 6803