title: Structure of the α-1,6/α-1,4-specific glucansucrase GTFA from Lactobacillus reuteri 121.
abstract: The reuteransucrase GTFA from Lactobacillus reuteri 121, which belongs to glycosyl hydrolase family GH70, synthesizes branched α-glucans with both α-1,6- and α-1,4-glycosidic linkages (reuteran) from sucrose. The crystal structure of GTFA-ΔN, a 118 kDa fragment of GTFA comprising residues 745-1763 and including the catalytic domain, was determined at 3.6 Å resolution by molecular replacement. The crystals have large solvent channels and an unusually high solvent content of 85%. GTFA-ΔN has the same domain arrangement and domain topologies as observed in previously determined GH70 glucansucrase structures. The architecture of the GTFA-ΔN active site and binding pocket confirms that glucansucrases have a conserved substrate specificity for sucrose. However, this first crystal structure of an α-1,6/α-1,4-specific glucansucrase shows that residues from conserved sequence motif IV (1128-1136 in GTFA-ΔN) contribute to the acceptor-binding subsites and that they display differences compared with other structurally characterized glucansucrases. In particular, the structure clarifies the importance of residues following the transition-state stabilizer for product specificity, and especially residue Asn1134, which is in a position to interact with sugar units in acceptor subsite +2.
authors.affiliation: Laboratory of Biophysical Chemistry, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Tjaard
authors.initials: T
authors.lastname: Pijning
authors.forename: Andreja
authors.initials: A
authors.lastname: Vujičić-Žagar
authors.forename: Slavko
authors.initials: S
authors.lastname: Kralj
authors.forename: Lubbert
authors.initials: L
authors.lastname: Dijkhuizen
authors.forename: Bauke W
authors.initials: BW
authors.lastname: Dijkstra
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D005936:Glucans / Q000737:chemistry / Q000378:metabolism; D016695:Glycosyltransferases / Q000737:chemistry* / Q000378:metabolism; D052200:Limosilactobacillus reuteri / Q000201:enzymology*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D013395:Sucrose / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005936:Glucans; D013395:Sucrose; D016695:Glycosyltransferases; C033837:alternansucrase