title: Mechanistic insights into validoxylamine A 7'-phosphate synthesis by VldE using the structure of the entire product complex.
abstract: The pseudo-glycosyltransferase VldE catalyzes non-glycosidic C-N coupling between an unsaturated cyclitol and a saturated aminocyclitol with the conservation of the stereochemical configuration of the substrates to form validoxylamine A 7'-phosphate, the biosynthetic precursor of the antibiotic validamycin A. To study the molecular basis of its mechanism, the three-dimensional structures of VldE from Streptomyces hygroscopicus subsp. limoneus was determined in apo form, in complex with GDP, in complex with GDP and validoxylamine A 7'-phosphate, and in complex with GDP and trehalose. The structure of VldE with the catalytic site in both an "open" and "closed" conformation is also described. With these structures, the preferred binding of the guanine moiety by VldE, rather than the uracil moiety as seen in OtsA could be explained. The elucidation of the VldE structure in complex with the entirety of its products provides insight into the internal return mechanism by which catalysis occurs with a net retention of the stereochemical configuration of the donated cyclitol.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Cavalier
authors.forename: Young-Sun
authors.initials: YS
authors.lastname: Yim
authors.forename: Shumpei
authors.initials: S
authors.lastname: Asamizu
authors.forename: David
authors.initials: D
authors.lastname: Neau
authors.forename: Khaled H
authors.initials: KH
authors.lastname: Almabruk
authors.forename: Taifo
authors.initials: T
authors.lastname: Mahmud
authors.forename: Yong-Hwan
authors.initials: YH
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D054812:Cyclitols / Q000378:metabolism; D016695:Glycosyltransferases / Q000737:chemistry* / Q000378:metabolism*; D007294:Inositol / Q000031:analogs & derivatives* / Q000096:biosynthesis; D007295:Inositol Phosphates / Q000096:biosynthesis*; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology
chemical_list: D054812:Cyclitols; D007295:Inositol Phosphates; D008024:Ligands; D009711:Nucleotides; C052534:validoxylamine A; D007294:Inositol; D016695:Glycosyltransferases