Biochemical and crystallographic characterization of a glucansucrase from Lactobacillus reuteri 180

Glucansucrases are large extracellular transglycosidases secreted by lactic acid bacteria. Using sucrose as a substrate they synthesize high molecular mass α-glucans or, in the presence of suitable acceptor molecules, low molecular mass oligosaccharides. Although about 60 glucansucrases have been classified in glycoside hydrolase family GH70, no three-dimensional structure has been reported for any. With the aim of solving the first structure of a GH70 glucansucrase, purification and crystallization experiments were performed with a fully active, 117 kDa N-terminally truncated fragment of glucansucrase GTF180 from Lactobacillus reuteri 180 (residues 742–1772). Crystallization experiments yielded crystals that belong to two different triclinic crystal forms (space group P1) and one orthorhombic crystal form (space group P2₁2₁2₁). Native data sets for both triclinic and the orthorhombic crystals were collected at 1.7 and 2.0 Å resolution, respectively. Enzyme activity assays, pH and temperature optima show comparable values for both the full-length and the N-terminally truncated GTF180.