3TTS

Crystal structure of beta-galactosidase from Bacillus circulans sp. alkalophilus

Summary for 3TTS

• Entry DOI: 10.2210/pdb3tts/pdb
• Related: 3TTY
• Descriptor: Beta-galactosidase, ZINC ION (3 entities in total)
• Functional Keywords: tim barrel, glycoside hydrolase, hydrolase
• Biological source: Bacillus circulans subsp. alkalophilus
• Total number of polymer chains: 6
• Total formula weight: 464872.61

Authors

Maksimainen, M.,Hakulinen, N.,Rouvinen, J. (deposition date: 2011-09-15, release date: 2012-03-21, Last modification date: 2023-09-13)

Primary citation

Maksimainen, M.,Paavilainen, S.,Hakulinen, N.,Rouvinen, J.
Structural analysis, enzymatic characterization, and catalytic mechanisms of beta-galactosidase from Bacillus circulans sp. alkalophilus.
Febs J., 279:1788-1798, 2012

PubMed Abstract: Crystal structures of native and α-D-galactose-bound Bacillus circulans sp. alkalophilus β-galactosidase (Bca-β-gal) were determined at 2.40 and 2.25 Å resolutions, respectively. Bca-β-gal is a member of family 42 of glycoside hydrolases, and forms a 460 kDa hexameric structure in crystal. The protein consists of three domains, of which the catalytic domain has an (α/β)(8) barrel structure with a cluster of sulfur-rich residues inside the β-barrel. The shape of the active site is clearly more open compared to the only homologous structure available in the Protein Data Bank. This is due to the number of large differences in the loops that connect the C-terminal ends of the β-strands to the N-terminal ends of the α-helices within the (α/β)(8) barrel. The complex structure shows that galactose binds to the active site as an α-anomer and induces clear conformational changes in the active site. The implications of α-D-galactose binding with respect to the catalytic mechanism are discussed. In addition, we suggest that β-galactosidases mainly utilize a reverse hydrolysis mechanism for synthesis of galacto-oligosaccharides.

PubMed: 22385475
DOI: 10.1111/j.1742-4658.2012.08555.x

Experimental method

X-RAY DIFFRACTION (2.401 Å)