title: Characterization of the N-methyltransferase CalM involved in calcimycin biosynthesis by Streptomyces chartreusis NRRL 3882.
abstract: Calcimycin is a rare divalent cation specific ionophore antibiotic that has many biochemical and pharmaceutical applications. We have recently cloned and sequenced the Streptomyces chartreusis calcimycin biosynthesis gene cluster as well as identified the genes required for the synthesis of the polyketide backbone of calcimycin. Additional modifying or decorating enzymes are required to convert the polyketide backbone into the biologically active calcimycin. Using targeted mutagenesis of Streptomyces we were able to show that calM from the calcimycin biosynthesis gene cluster is required for calcimycin production. Inactivating calM by PCR targeting, caused high level accumulation of N-demethyl calcimycin. CalM in the presence of S-adenosyl-L-methionine converted N-demethyl calcimycin to calcimycin in vitro. The enzyme was determined to have a kinetic parameter of Km 276 μM, kcat 1.26 min(-1) and kcat/Km 76.2 M(-1) s(-1). These results proved that CalM is a N-methyltransferase that is required for calcimycin biosynthesis, and they set the stage for generating much desired novel calcimycin derivatives by rational genetic and chemical engineering.
authors.affiliation: State Key Laboratory of Microbial Metabolism, School of Life Science & Biotechnology, Shanghai Jiaotong University, Shanghai 200030, People's Republic of China.
authors.forename: Qiulin
authors.initials: Q
authors.lastname: Wu
authors.forename: Lixia
authors.initials: L
authors.lastname: Gou
authors.forename: Shuangjun
authors.initials: S
authors.lastname: Lin
authors.forename: Jingdan
authors.initials: J
authors.lastname: Liang
authors.forename: Jun
authors.initials: J
authors.lastname: Yin
authors.forename: Xiufen
authors.initials: X
authors.lastname: Zhou
authors.forename: Linquan
authors.initials: L
authors.lastname: Bai
authors.forename: Derong
authors.initials: D
authors.lastname: An
authors.forename: Zixin
authors.initials: Z
authors.lastname: Deng
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D000001:Calcimycin / Q000096:biosynthesis*; D007700:Kinetics; D008780:Methyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D013302:Streptomyces / Q000201:enzymology* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D000001:Calcimycin; D008780:Methyltransferases