Acta Crystallographica Section D

Biological Crystallography

Volume 69, Part 3 (March 2013)


research papers



Acta Cryst. (2013). D69, 451-463    [ doi:10.1107/S0907444912049608 ]

GH1-family 6-P-[beta]-glucosidases from human microbiome lactic acid bacteria

K. Michalska, K. Tan, H. Li, C. Hatzos-Skintges, J. Bearden, G. Babnigg and A. Joachimiak

Abstract: In lactic acid bacteria and other bacteria, carbohydrate uptake is mostly governed by phosphoenolpyruvate-dependent phosphotransferase systems (PTSs). PTS-dependent translocation through the cell membrane is coupled with phosphorylation of the incoming sugar. After translocation through the bacterial membrane, the [beta]-glycosidic bond in 6'-P-[beta]-glucoside is cleaved, releasing 6-P-[beta]-glucose and the respective aglycon. This reaction is catalyzed by 6-P-[beta]-glucosidases, which belong to two glycoside hydrolase (GH) families: GH1 and GH4. Here, the high-resolution crystal structures of GH1 6-P-[beta]-glucosidases from Lactobacillus plantarum (LpPbg1) and Streptococcus mutans (SmBgl) and their complexes with ligands are reported. Both enzymes show hydrolytic activity towards 6'-P-[beta]-glucosides. The LpPbg1 structure has been determined in an apo form as well as in a complex with phosphate and a glucose molecule corresponding to the aglycon molecule. The S. mutans homolog contains a sulfate ion in the phosphate-dedicated subcavity. SmBgl was also crystallized in the presence of the reaction product 6-P-[beta]-glucose. For a mutated variant of the S. mutans enzyme (E375Q), the structure of a 6'-P-salicin complex has also been determined. The presence of natural ligands enabled the definition of the structural elements that are responsible for substrate recognition during catalysis.

PDB references: 3qom, 4gze, 3pn8, 4f66 and 4f79

Keywords: 6-P-[beta]-glucosidases; glycoside hydrolases; GH1; cellobiose; gentiobiose; salicin.


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