title: A base-flipping mechanism for the T4 phage beta-glucosyltransferase and identification of a transition-state analog.
abstract: T4 phage beta-glucosyltransferase (BGT) modifies T4 DNA. We crystallized BGT with UDP-glucose and a 13mer DNA fragment containing an abasic site. We obtained two crystal structures of a ternary complex BGT-UDP-DNA at 1.8A and 2.5A resolution, one with a Tris molecule and the other with a metal ion at the active site. Both structures reveal a large distortion in the bound DNA. BGT flips the deoxyribose moiety at the abasic site to an extra-helical position and induces a 40 degrees bend in the DNA with a marked widening of the major groove. The Tris molecule mimics the glucose moiety in its transition state. The base-flipping mechanism, which has so far been observed only for glycosylases, methyltransferases and endonucleases, is now reported for a glucosyltransferase. BGT is unique in binding and inserting a loop into the DNA duplex through the major groove only. Furthermore, BGT compresses the backbone DNA one base further than the target base on the 3'-side.
authors.affiliation: Laboratoire d'Enzymologie et Biochimie Structurales, UPR 9063 CNRS, Bât. 34, 1 Avenue de la Terrasse, 91198, Gif-sur-Yvette, France
authors.forename: Laurent
authors.initials: L
authors.lastname: Larivière
authors.forename: Solange
authors.initials: S
authors.lastname: Moréra
mesh_terms: D017122:Bacteriophage T4 / Q000201:enzymology*; D020029:Base Pairing; D001665:Binding Sites; D002384:Catalysis; D003460:Crystallization; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D005964:Glucosyltransferases / Q000737:chemistry* / Q000378:metabolism*; D008670:Metals / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D014325:Tromethamine / Q000737:chemistry / Q000378:metabolism; D014532:Uridine Diphosphate Glucose / Q000737:chemistry / Q000378:metabolism
chemical_list: D008670:Metals; D014325:Tromethamine; D004247:DNA; D005964:Glucosyltransferases; C026585:DNA beta-glucosyltransferase; D014532:Uridine Diphosphate Glucose