title: A structural basis for the allosteric regulation of non-hydrolysing UDP-GlcNAc 2-epimerases.
abstract: The non-hydrolysing bacterial UDP-N-acetylglucosamine 2-epimerase (UDP-GlcNAc 2-epimerase) catalyses the conversion of UDP-GlcNAc into UDP-N-acetylmannosamine, an intermediate in the biosynthesis of several cell-surface polysaccharides. This enzyme is allosterically regulated by its substrate UDP-GlcNAc. The structure of the ternary complex between the Bacillus anthracis UDP-GlcNAc 2-epimerase, its substrate UDP-GlcNAc and the reaction intermediate UDP, showed direct interactions between UDP and its substrate, and between the complex and highly conserved enzyme residues, identifying the allosteric site of the enzyme. The binding of UDP-GlcNAc is associated with conformational changes in the active site of the enzyme. Kinetic data and mutagenesis of the highly conserved UDP-GlcNAc-interacting residues confirm their importance in the substrate binding and catalysis of the enzyme. This constitutes the first example to our knowledge, of an enzymatic allosteric activation by direct interaction between the substrate and the allosteric activator.
authors.affiliation: Laboratory of Structural Microbiology, The Rockfeller University, New York, NY 10021, USA.
authors.forename: Lucas M
authors.initials: LM
authors.lastname: Velloso
authors.forename: Shyam S
authors.initials: SS
authors.lastname: Bhaskaran
authors.forename: Raymond
authors.initials: R
authors.lastname: Schuch
authors.forename: Vincent A
authors.initials: VA
authors.lastname: Fischetti
authors.forename: C Erec
authors.initials: CE
authors.lastname: Stebbins
mesh_terms: D000494:Allosteric Regulation; D001408:Bacillus anthracis / Q000201:enzymology* / Q000254:growth & development; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002238:Carbohydrate Epimerases / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D018360:Crystallography, X-Ray; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000737:chemistry / Q000378:metabolism
chemical_list: D014537:Uridine Diphosphate N-Acetylglucosamine; D002238:Carbohydrate Epimerases; C100033:UDP acetylglucosamine-2-epimerase