title: Structural and functional characterization of CalS11, a TDP-rhamnose 3'-O-methyltransferase involved in calicheamicin biosynthesis.
abstract: Sugar methyltransferases (MTs) are an important class of tailoring enzymes that catalyze the transfer of a methyl group from S-adenosyl-l-methionine to sugar-based N-, C- and O-nucleophiles. While sugar N- and C-MTs involved in natural product biosynthesis have been found to act on sugar nucleotide substrates prior to a subsequent glycosyltransferase reaction, corresponding sugar O-methylation reactions studied thus far occur after the glycosyltransfer reaction. Herein we report the first in vitro characterization using (1)H-(13)C-gHSQC with isotopically labeled substrates and the X-ray structure determination at 1.55 Å resolution of the TDP-3'-O-rhamnose-methyltransferase CalS11 from Micromonospora echinospora. This study highlights a unique NMR-based methyltransferase assay, implicates CalS11 to be a metal- and general acid/base-dependent O-methyltransferase, and as a first crystal structure for a TDP-hexose-O-methyltransferase, presents a new template for mechanistic studies and/or engineering.
authors.affiliation: Center for Pharmaceutical Research and Innovation, University of Kentucky College of Pharmacy , Lexington, Kentucky 40536, United States.
authors.forename: Shanteri
authors.initials: S
authors.lastname: Singh
authors.forename: Aram
authors.initials: A
authors.lastname: Chang
authors.forename: Kate E
authors.initials: KE
authors.lastname: Helmich
authors.forename: Craig A
authors.initials: CA
authors.lastname: Bingman
authors.forename: Russell L
authors.initials: RL
authors.lastname: Wrobel
authors.forename: Emily T
authors.initials: ET
authors.lastname: Beebe
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Makino
authors.forename: David J
authors.initials: DJ
authors.lastname: Aceti
authors.forename: Kevin
authors.initials: K
authors.lastname: Dyer
authors.forename: Greg L
authors.initials: GL
authors.lastname: Hura
authors.forename: Manjula
authors.initials: M
authors.lastname: Sunkara
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Morris
authors.forename: George N
authors.initials: GN
authors.lastname: Phillips
authors.forename: Jon S
authors.initials: JS
authors.lastname: Thorson
mesh_terms: D000617:Aminoglycosides / Q000096:biosynthesis*; D002384:Catalysis; D020134:Catalytic Domain; D053281:Enediynes; D009682:Magnetic Resonance Spectroscopy; D008780:Methyltransferases / Q000737:chemistry* / Q000378:metabolism*; D008847:Micromonospora / Q000201:enzymology; D008958:Models, Molecular; D015394:Molecular Structure; D012210:Rhamnose / Q000737:chemistry*
chemical_list: D000617:Aminoglycosides; D053281:Enediynes; C074528:calicheamicin T; D008780:Methyltransferases; D012210:Rhamnose