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Crystal structure of a 117 kDa glucansucrase fragment provides insight into evolution and product specificity of GH70 enzymes

Vujičić-Žagar, A., Pijning, T., Kralj, S., López, C. A., Eeuwema, W., Dijkhuizen, L. & Dijkstra, B. W., 14-Dec-2010, In : Proceedings of the National Academy of Sciences of the United States of America. 107, 50, p. 21406-21411 6 p.

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Glucansucrases are large enzymes belonging to glycoside hydrolase family 70, which catalyze the cleavage of sucrose into fructose and glucose, with the concomitant transfer of the glucose residue to a growing α-glucan polymer. Among others, plaque-forming oral bacteria secrete these enzymes to produce α-glucans, which facilitate the adhesion of the bacteria to the tooth enamel. We determined the crystal structure of a fully active, 1,031-residue fragment encompassing the catalytic and C-terminal domains of GTF180 from Lactobacillus reuteri 180, both in the native state, and in complexes with sucrose and maltose. These structures show that the enzyme has an α-amylase-like (β∕α)8-barrel catalytic domain that is circularly permuted compared to the catalytic domains of members of glycoside hydrolase families 13 and 77, which belong to the same GH-H superfamily. In contrast to previous suggestions, the enzyme has only one active site and one nucleophilic residue. Surprisingly, in GTF180 the peptide chain follows a “U”-path, such that four of the five domains are made up from discontiguous N- and C-terminal stretches of the peptide chain. Finally, the structures give insight into the factors that determine the different linkage types in the polymeric product.
Original languageEnglish
Pages (from-to)21406-21411
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume107
Issue number50
Publication statusPublished - 14-Dec-2010

    Keywords

  • crystal structure complexes, exopolysaccharide, Lactobacillus reuteri, dental caries, ALPHA-AMYLASE FAMILY, CYCLODEXTRIN GLYCOSYLTRANSFERASE, COVALENT INTERMEDIATE, GLYCOSYL HYDROLASES, PROTEIN TOPOLOGIES, MECHANISM, DEXTRANSUCRASE, LACTOBACILLUS, GLUCOSYLTRANSFERASE, TRANSGLYCOSYLASE

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