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Title: Molecular Dissection of Xyloglucan Recognition in a Prominent Human Gut Symbiont

Polysaccharide utilization loci (PUL) within the genomes of resident human gutBacteroidetesare central to the metabolism of the otherwise indigestible complex carbohydrates known as “dietary fiber.” However, functional characterization of PUL lags significantly behind sequencing efforts, which limits physiological understanding of the human-bacterial symbiosis. In particular, the molecular basis of complex polysaccharide recognition, an essential prerequisite to hydrolysis by cell surface glycosidases and subsequent metabolism, is generally poorly understood. Here, we present the biochemical, structural, and reverse genetic characterization of two unique cell surface glycan-binding proteins (SGBPs) encoded by a xyloglucan utilization locus (XyGUL) fromBacteroides ovatus, which are integral to growth on this key dietary vegetable polysaccharide. Biochemical analysis reveals that these outer membrane-anchored proteins are in fact exquisitely specific for the highly branched xyloglucan (XyG) polysaccharide. The crystal structure of SGBP-A, a SusD homolog, with a bound XyG tetradecasaccharide reveals an extended carbohydrate-binding platform that primarily relies on recognition of the β-glucan backbone. The unique, tetra-modular structure of SGBP-B is comprised of tandem Ig-like folds, with XyG binding mediated at the distal C-terminal domain. Despite displaying similar affinities for XyG, reverse-genetic analysis reveals that SGBP-B is only required for the efficient capture of smaller oligosaccharides, whereas the presence of SGBP-Amore » is more critical than its carbohydrate-binding ability for growth on XyG. Finally, together, these data demonstrate that SGBP-A and SGBP-B play complementary, specialized roles in carbohydrate capture byB. ovatusand elaborate a model of how vegetable xyloglucans are accessed by theBacteroidetes.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [4] ;  [4] ;  [5] ;  [1] ;  [3]
  1. Univ. of British Columbia, Vancouver, BC (Canada). Michael Smith Lab. and Dept. of Chemistry
  2. Univ. of Michigan, Ann Arbor, MI (United States). Medical School, Dept. of Microbiology and Immunology
  3. Univ. of Michigan, Ann Arbor, MI (United States). Medical School, Dept. of Microbiology and Immunology
  4. Univ. of British Columbia, Vancouver, BC (Canada). Michael Smith Lab., Dept. of Chemical and Biological Engineering
  5. Northwestern Univ., Argonne, IL (United States). Synchrotron Research Center
Publication Date:
Grant/Contract Number:
AC02-06CH11357; MOP-137134; MOP-142472; 085P1000817
Type:
Accepted Manuscript
Journal Name:
mBio (Online)
Additional Journal Information:
Journal Name: mBio (Online); Journal Volume: 7; Journal Issue: 2; Journal ID: ISSN 2150-7511
Publisher:
American Society for Microbiology
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC); Natural Sciences and Engineering Research Council of Canada (NSERC); Canadian Institutes of Health Research (CIHR)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1376061

Tauzin, Alexandra S., Kwiatkowski, Kurt J., Orlovsky, Nicole I., Smith, Christopher J., Creagh, A. Louise, Haynes, Charles A., Wawrzak, Zdzislaw, Brumer, Harry, and Koropatkin, Nicole M.. Molecular Dissection of Xyloglucan Recognition in a Prominent Human Gut Symbiont. United States: N. p., Web. doi:10.1128/mBio.02134-15.
Tauzin, Alexandra S., Kwiatkowski, Kurt J., Orlovsky, Nicole I., Smith, Christopher J., Creagh, A. Louise, Haynes, Charles A., Wawrzak, Zdzislaw, Brumer, Harry, & Koropatkin, Nicole M.. Molecular Dissection of Xyloglucan Recognition in a Prominent Human Gut Symbiont. United States. doi:10.1128/mBio.02134-15.
Tauzin, Alexandra S., Kwiatkowski, Kurt J., Orlovsky, Nicole I., Smith, Christopher J., Creagh, A. Louise, Haynes, Charles A., Wawrzak, Zdzislaw, Brumer, Harry, and Koropatkin, Nicole M.. 2016. "Molecular Dissection of Xyloglucan Recognition in a Prominent Human Gut Symbiont". United States. doi:10.1128/mBio.02134-15. https://www.osti.gov/servlets/purl/1376061.
@article{osti_1376061,
title = {Molecular Dissection of Xyloglucan Recognition in a Prominent Human Gut Symbiont},
author = {Tauzin, Alexandra S. and Kwiatkowski, Kurt J. and Orlovsky, Nicole I. and Smith, Christopher J. and Creagh, A. Louise and Haynes, Charles A. and Wawrzak, Zdzislaw and Brumer, Harry and Koropatkin, Nicole M.},
abstractNote = {Polysaccharide utilization loci (PUL) within the genomes of resident human gutBacteroidetesare central to the metabolism of the otherwise indigestible complex carbohydrates known as “dietary fiber.” However, functional characterization of PUL lags significantly behind sequencing efforts, which limits physiological understanding of the human-bacterial symbiosis. In particular, the molecular basis of complex polysaccharide recognition, an essential prerequisite to hydrolysis by cell surface glycosidases and subsequent metabolism, is generally poorly understood. Here, we present the biochemical, structural, and reverse genetic characterization of two unique cell surface glycan-binding proteins (SGBPs) encoded by a xyloglucan utilization locus (XyGUL) fromBacteroides ovatus, which are integral to growth on this key dietary vegetable polysaccharide. Biochemical analysis reveals that these outer membrane-anchored proteins are in fact exquisitely specific for the highly branched xyloglucan (XyG) polysaccharide. The crystal structure of SGBP-A, a SusD homolog, with a bound XyG tetradecasaccharide reveals an extended carbohydrate-binding platform that primarily relies on recognition of the β-glucan backbone. The unique, tetra-modular structure of SGBP-B is comprised of tandem Ig-like folds, with XyG binding mediated at the distal C-terminal domain. Despite displaying similar affinities for XyG, reverse-genetic analysis reveals that SGBP-B is only required for the efficient capture of smaller oligosaccharides, whereas the presence of SGBP-A is more critical than its carbohydrate-binding ability for growth on XyG. Finally, together, these data demonstrate that SGBP-A and SGBP-B play complementary, specialized roles in carbohydrate capture byB. ovatusand elaborate a model of how vegetable xyloglucans are accessed by theBacteroidetes.},
doi = {10.1128/mBio.02134-15},
journal = {mBio (Online)},
number = 2,
volume = 7,
place = {United States},
year = {2016},
month = {4}
}