期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 292, 期 52, 页码 21690-21702出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.RA117.000106
关键词
Arabidopsis thaliana; enzyme kinetics; X-ray crystallography; protein structure; S-adenosylmethionine (SAM)
资金
- Department of Energy Office of Biological and Environmental Research [DE-AC02-06CH11357]
- National Science Foundation [EPS 0236913, MCB 045531, DBI 0521587]
- Kansas Technology Enterprise Corp.
- K-IDeA Networks of Biomedical Research Excellence (INBRE) of National Institute of Health [P20RR16475]
- Kansas State University
Phosphocholine (pCho) is a precursor for phosphatidylcholine and osmoprotectants in plants. In plants, de novo synthesis of pCho relies on the phosphobase methylation pathway. Phosphoethanolamine methyltransferase (PMT) catalyzes the triple methylation of phosphoethanolamine (pEA) to pCho. The plant PMTs are di-domain methyltransferases that divide the methylation of pEA in one domain from subsequent methylations in the second domain. To understand the molecular basis of this architecture, we examined the biochemical properties of three Arabidopsis thaliana PMTs (AtPMT1-3) and determined the X-ray crystal structures of AtPMT1 and AtPMT2. Although each isoform synthesizes pCho from pEA, their physiological roles differ with AtPMT1 essential for normal growth and salt tolerance, whereas AtPMT2 and AtPMT3 overlap functionally. The structures of AtPMT1 and AtPMT2 reveal unique features in each methyltransferase domain, including active sites that use different chemical mechanisms for phosphobase methylation. These structures also show how rearrangements in both the active sites and the di-domain linker form catalytically competent active sites and provide insight on the evolution of the PMTs in plants, nematodes, and apicomplexans. Connecting conformational changes with catalysis in modular enzymes, like the PMT, provides new insights on interdomain communication in biosynthetic systems.
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