4E8C

Crystal structure of streptococcal beta-galactosidase in complex with galactose

4E8C の概要

• エントリーDOI: 10.2210/pdb4e8c/pdb
• 関連するPDBエントリー: 4E8D
• 分子名称: Glycosyl hydrolase, family 35, beta-D-galactopyranose, GLYCEROL, ... (4 entities in total)
• 機能のキーワード: tim barrel, beta-propeller, glycohydrolase, hydrolase
• 由来する生物種: Streptococcus pneumoniae
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 139781.61

構造登録者

Cheng, W.,Wang, L.,Bai, X.H.,Jiang, Y.L.,Li, Q.,Yu, G.,Zhou, C.Z.,Chen, Y.X. (登録日: 2012-03-20, 公開日: 2012-05-30, 最終更新日: 2023-11-08)

主引用文献

Cheng, W.,Wang, L.,Jiang, Y.L.,Bai, X.H.,Chu, J.,Li, Q.,Yu, G.,Liang, Q.L.,Zhou, C.Z.,Chen, Y.X.
Structural insights into the substrate specificity of Streptococcus pneumoniae beta (1,3)-galactosidase BgaC
J.Biol.Chem., 287:22910-22918, 2012

PubMed Abstract: The surface-exposed β-galactosidase BgaC from Streptococcus pneumoniae was reported to be a virulence factor because of its specific hydrolysis activity toward the β(1,3)-linked galactose and N-acetylglucosamine (Galβ(1,3)NAG) moiety of oligosaccharides on the host molecules. Here we report the crystal structure of BgaC at 1.8 Å and its complex with galactose at 1.95 Å. At pH 5.5-8.0, BgaC exists as a stable homodimer, each subunit of which consists of three distinct domains: a catalytic domain of a classic (β/α)(8) TIM barrel, followed by two all-β domains (ABDs) of unknown function. The side walls of the TIM β-barrel and a loop extended from the first ABD constitute the active site. Superposition of the galactose-complexed structure to the apo-form revealed significant conformational changes of residues Trp-243 and Tyr-455. Simulation of a putative substrate entrance tunnel and modeling of a complex structure with Galβ(1,3)NAG enabled us to assign three key residues to the specific catalysis. Site-directed mutagenesis in combination with activity assays further proved that residues Trp-240 and Tyr-455 contribute to stabilizing the N-acetylglucosamine moiety, whereas Trp-243 is critical for fixing the galactose ring. Moreover, we propose that BgaC and other galactosidases in the GH-35 family share a common domain organization and a conserved substrate-determinant aromatic residue protruding from the second domain.

PubMed: 22593580
DOI: 10.1074/jbc.M112.367128

実験手法

X-RAY DIFFRACTION (1.95 Å)