title: Structural insights into the catalytic mechanism of Synechocystis magnesium protoporphyrin IX O-methyltransferase (ChlM).
abstract: Magnesium protoporphyrin IX O-methyltransferase (ChlM) catalyzes transfer of the methyl group from S-adenosylmethionine to the carboxyl group of the C13 propionate side chain of magnesium protoporphyrin IX. This reaction is the second committed step in chlorophyll biosynthesis from protoporphyrin IX. Here we report the crystal structures of ChlM from the cyanobacterium Synechocystis sp. PCC 6803 in complex with S-adenosylmethionine and S-adenosylhomocysteine at resolutions of 1.6 and 1.7 Å, respectively. The structures illustrate the molecular basis for cofactor and substrate binding and suggest that conformational changes of the two "arm" regions may modulate binding and release of substrates/products to and from the active site. Tyr-28 and His-139 were identified to play essential roles for methyl transfer reaction but are not indispensable for cofactor/substrate binding. Based on these structural and functional findings, a catalytic model is proposed.
authors: From the Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China, the University of Chinese Academy of Sciences, Beijing, 100049, China.
authors: Xuemin
authors: X
authors: Chen
authors: From the Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China, the University of Chinese Academy of Sciences, Beijing, 100049, China.
authors: Xiao
authors: X
authors: Wang
authors: From the Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China, the University of Chinese Academy of Sciences, Beijing, 100049, China.
authors: Juan
authors: J
authors: Feng
authors: From the Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
authors: Yuhong
authors: Y
authors: Chen
authors: From the Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China, the University of Chinese Academy of Sciences, Beijing, 100049, China.
authors: Ying
authors: Y
authors: Fang
authors: From the Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China, the University of Chinese Academy of Sciences, Beijing, 100049, China.
authors: Shun
authors: S
authors: Zhao
authors: From the Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China, the University of Chinese Academy of Sciences, Beijing, 100049, China.
authors: Aiguo
authors: A
authors: Zhao
authors: the Engineering Research Center for Biomedical Materials, School of Life Sciences, Anhui University, Hefei, Anhui, 230601, China, and.
authors: Min
authors: M
authors: Zhang
authors: From the Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China, liulin@ibcas.ac.cn.
authors: Lin
authors: L
authors: Liu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D002734:Chlorophyll / Q000096:biosynthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D007700:Kinetics; D008780:Methyltransferases / Q000737:chemistry* / Q000378:metabolism; D010788:Photosynthesis; D011487:Protein Conformation; D012436:S-Adenosylmethionine / Q000737:chemistry; D013379:Substrate Specificity; D046939:Synechocystis / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D002734:Chlorophyll; D012436:S-Adenosylmethionine; D008780:Methyltransferases; C100792:chlM protein, Synechocystis sp.
keywords: Chlorophyll; Chloroplast; Enzyme Mechanism; Enzyme Structure; Photosynthesis; Protein Structure