Cold-active beta-galactosidase

Years: 2002-now

PDB code: 1YQ2

Beta-galactosidases catalyze, except other, cleavage of lactose to galactose and glucose and are therefore used in food industry. Arthrobacter sp. C2-2, a soil bacterium found on an island near Antarctica, belongs to psychrotrophic, i.e. cold tolerant, microorganisms. Two beta-galactosidases, isoenzymes C-2-2-1 and C-2-2-2, were isolated from this bacterium. Structure of C-2-2-1 beta-galactosidase from Arthrobacter sp. C2-2 was solved at 1.9 Å resolution.

The beta-galactosidase belongs to glycosyl hydrolase structural family 2. It consists of five domains; the active site of the beta-galactosidase is localized within the TIM barrel domain. It has 30% sequence identity with Escherichia coli beta-galactosidase. In spite of the chain similarity, both enzymes differ in their oligomerization states; it may be connected with cold adaptation of the enzyme from Arthrobacter species. E. coli beta-galactosidase forms tetramers necessary for its function, while Arthrobacter galactosidase forms compact hexamers with active sites oriented into an internal cavity, connected by three types of channels with exterior solvent. There are also significant differences in the active sites of both enzymes.

Fig. 1. Cold-active beta-galactosidase from Arthrobacter sp. C2-2. Catalytic residues are denoted as black spheres.

Fig. 2. In the internal cavity of the galactosidase hexamer, beautiful nets of localized water molecules are observable.

Publications:

• • Skalova, T; Dohnalek, J; Spiwok, V; Lipovova, P; Vondrackova, E; Petrokova, H; Duskova, J; Strnad, H; Kralova, B; Hasek, J. Cold-active beta-galactosidase from Arthrobacter sp C2-2 forms compact 660 kDa hexamers: Crystal structure at 1.9 angstrom resolution. JOURNAL OF MOLECULAR BIOLOGY, 2005, 353(2), 282-294

  • Spiwok, V; Lipovova, P; Skalova, T; Duskova, J; Dohnalek, J; Hasek, J; Russell, NJ; Kralova, B. Cold-active enzymes studied by comparative molecular dynamics simulation. J MOL MODEL, 2007, 13, 485-497.

  • Spiwok, V; Lipovova, P; Skalova, T; Vondrackova, E; Dohnalek, J; Hasek, J; Kralova, B. Modelling of carbohydrate-aromatic interactions: ab initio energetics and force field performance. JOURNAL OF COMPUTER-AIDED MOLECULAR DESIGN, 2005, 19(12), 887-901