GH1-family 6-P-β-glucosidases from human microbiome lactic acid bacteria

Acta Crystallogr D Biol Crystallogr. 2013 Mar;69(Pt 3):451-63. doi: 10.1107/S0907444912049608. Epub 2013 Feb 16.

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 β-glycosidic bond in 6'-P-β-glucoside is cleaved, releasing 6-P-β-glucose and the respective aglycon. This reaction is catalyzed by 6-P-β-glucosidases, which belong to two glycoside hydrolase (GH) families: GH1 and GH4. Here, the high-resolution crystal structures of GH1 6-P-β-glucosidases from Lactobacillus plantarum (LpPbg1) and Streptococcus mutans (SmBgl) and their complexes with ligands are reported. Both enzymes show hydrolytic activity towards 6'-P-β-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-β-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.

Keywords: 6-P-β-glucosidases; GH1; cellobiose; gentiobiose; glycoside hydrolases; salicin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Crystallography, X-Ray
  • Glucosidases / chemistry*
  • Glucosidases / genetics
  • Glucosidases / metabolism
  • Humans
  • Lactobacillus plantarum / enzymology*
  • Lactobacillus plantarum / genetics
  • Lactobacillus plantarum / metabolism
  • Ligands
  • Metagenome*
  • Phosphoenolpyruvate Sugar Phosphotransferase System / chemistry*
  • Streptococcus mutans / enzymology*
  • Streptococcus mutans / genetics

Substances

  • Ligands
  • Phosphoenolpyruvate Sugar Phosphotransferase System
  • Glucosidases
  • 6-phospho-beta-glucosidase

Associated data

  • PDB/3PN8
  • PDB/3QOM
  • PDB/4F66
  • PDB/4F79
  • PDB/4GZE