title: Structural characterization of the mitomycin 7-O-methyltransferase.
abstract: Mitomycins are quinone-containing antibiotics, widely used as antitumor drugs in chemotherapy. Mitomycin-7-O-methyltransferase (MmcR), a key tailoring enzyme involved in the biosynthesis of mitomycin in Streptomyces lavendulae, catalyzes the 7-O-methylation of both C9β- and C9α-configured 7-hydroxymitomycins. We have determined the crystal structures of the MmcR-S-adenosylhomocysteine (SAH) binary complex and MmcR-SAH-mitomycin A (MMA) ternary complex at resolutions of 1.9and 2.3 Å, respectively. The study revealed MmcR to adopt a common S-adenosyl-L-methionine-dependent O-methyltransferase fold and the presence of a structurally conserved active site general acid-base pair is consistent with a proton-assisted methyltransfer common to most methyltransferases. Given the importance of C7 alkylation to modulate mitomycin redox potential, this study may also present a template toward the future engineering of catalysts to generate uniquely bioactive mitomycins.
authors.affiliation: Division of Pharmaceutical Sciences, Wisconsin Center for Natural Product Research, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA.
authors.forename: Shanteri
authors.initials: S
authors.lastname: Singh
authors.forename: Aram
authors.initials: A
authors.lastname: Chang
authors.forename: Randal D
authors.initials: RD
authors.lastname: Goff
authors.forename: Craig A
authors.initials: CA
authors.lastname: Bingman
authors.forename: Sabine
authors.initials: S
authors.lastname: Grüschow
authors.forename: David H
authors.initials: DH
authors.lastname: Sherman
authors.forename: George N
authors.initials: GN
authors.lastname: Phillips
authors.forename: Jon S
authors.initials: JS
authors.lastname: Thorson
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001665:Binding Sites; D018360:Crystallography, X-Ray; D008780:Methyltransferases / Q000737:chemistry* / Q000378:metabolism; D016685:Mitomycin / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012435:S-Adenosylhomocysteine / Q000737:chemistry* / Q000378:metabolism; D016415:Sequence Alignment; D013302:Streptomyces / Q000201:enzymology; D040681:Structural Homology, Protein
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D016685:Mitomycin; D012435:S-Adenosylhomocysteine; D008780:Methyltransferases