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Title: Apo- and Cellopentaose-bound Structures of the Bacterial Cellulose Synthase Subunit BcsZ

Abstract

Cellulose, a very abundant extracellular polysaccharide, is synthesized in a finely tuned process that involves the activity of glycosyl-transferases and hydrolases. The cellulose microfibril consists of bundles of linear {beta}-1,4-glucan chains that are synthesized inside the cell; however, the mechanism by which these polymers traverse the cell membrane is currently unknown. In Gram-negative bacteria, the cellulose synthase complex forms a trans-envelope complex consisting of at least four subunits. Although three of these subunits account for the synthesis and translocation of the polysaccharide, the fourth subunit, BcsZ, is a periplasmic protein with endo-{beta}-1,4-glucanase activity. BcsZ belongs to family eight of glycosyl-hydrolases, and its activity is required for optimal synthesis and membrane translocation of cellulose. In this study we report two crystal structures of BcsZ from Escherichia coli. One structure shows the wild-type enzyme in its apo form, and the second structure is for a catalytically inactive mutant of BcsZ in complex with the substrate cellopentaose. The structures demonstrate that BcsZ adopts an ({alpha}/{alpha}){sub 6}-barrel fold and that it binds four glucan moieties of cellopentaose via highly conserved residues exclusively on the nonreducing side of its catalytic center. Thus, the BcsZ-cellopentaose structure most likely represents a posthydrolysis state in which the newlymore » formed nonreducing end has already left the substrate binding pocket while the enzyme remains attached to the truncated polysaccharide chain. We further show that BcsZ efficiently degrades {beta}-1,4-glucans in in vitro cellulase assays with carboxymethyl-cellulose as substrate.« less

Authors:
;  [1]
  1. (UV)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
UNIVERSITY
OSTI Identifier:
1040893
Resource Type:
Journal Article
Journal Name:
J. Biol. Chem.
Additional Journal Information:
Journal Volume: 286; Journal Issue: (20) ; 05, 2011; Journal ID: ISSN 0021-9258
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES; BACTERIA; CELL MEMBRANES; CELLULASE; CELLULOSE; CRYSTAL STRUCTURE; ENZYMES; ESCHERICHIA COLI; GLYCOSYL HYDROLASES; GLYCOSYL TRANSFERASES; HYDROLASES; IN VITRO; MEMBRANES; MUTANTS; POLYMERS; POLYSACCHARIDES; PROTEIN STRUCTURE; PROTEINS; RESIDUES; SUBSTRATES; SYNTHESIS; TRANSLOCATION

Citation Formats

Mazur, Olga, and Zimmer, Jochen. Apo- and Cellopentaose-bound Structures of the Bacterial Cellulose Synthase Subunit BcsZ. United States: N. p., 2012. Web. doi:10.1074/jbc.M111.227660.
Mazur, Olga, & Zimmer, Jochen. Apo- and Cellopentaose-bound Structures of the Bacterial Cellulose Synthase Subunit BcsZ. United States. doi:10.1074/jbc.M111.227660.
Mazur, Olga, and Zimmer, Jochen. Thu . "Apo- and Cellopentaose-bound Structures of the Bacterial Cellulose Synthase Subunit BcsZ". United States. doi:10.1074/jbc.M111.227660.
@article{osti_1040893,
title = {Apo- and Cellopentaose-bound Structures of the Bacterial Cellulose Synthase Subunit BcsZ},
author = {Mazur, Olga and Zimmer, Jochen},
abstractNote = {Cellulose, a very abundant extracellular polysaccharide, is synthesized in a finely tuned process that involves the activity of glycosyl-transferases and hydrolases. The cellulose microfibril consists of bundles of linear {beta}-1,4-glucan chains that are synthesized inside the cell; however, the mechanism by which these polymers traverse the cell membrane is currently unknown. In Gram-negative bacteria, the cellulose synthase complex forms a trans-envelope complex consisting of at least four subunits. Although three of these subunits account for the synthesis and translocation of the polysaccharide, the fourth subunit, BcsZ, is a periplasmic protein with endo-{beta}-1,4-glucanase activity. BcsZ belongs to family eight of glycosyl-hydrolases, and its activity is required for optimal synthesis and membrane translocation of cellulose. In this study we report two crystal structures of BcsZ from Escherichia coli. One structure shows the wild-type enzyme in its apo form, and the second structure is for a catalytically inactive mutant of BcsZ in complex with the substrate cellopentaose. The structures demonstrate that BcsZ adopts an ({alpha}/{alpha}){sub 6}-barrel fold and that it binds four glucan moieties of cellopentaose via highly conserved residues exclusively on the nonreducing side of its catalytic center. Thus, the BcsZ-cellopentaose structure most likely represents a posthydrolysis state in which the newly formed nonreducing end has already left the substrate binding pocket while the enzyme remains attached to the truncated polysaccharide chain. We further show that BcsZ efficiently degrades {beta}-1,4-glucans in in vitro cellulase assays with carboxymethyl-cellulose as substrate.},
doi = {10.1074/jbc.M111.227660},
journal = {J. Biol. Chem.},
issn = {0021-9258},
number = (20) ; 05, 2011,
volume = 286,
place = {United States},
year = {2012},
month = {10}
}