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A surface-exposed GH26 -mannanase from Bacteroides ovatus : Structure, role, and phylogenetic analysis of BoMan26B

Bågenholm, Viktoria LU ; Wiemann, Mathias LU ; Reddy, Sumitha K.; Bhattacharya, Abhishek; Rosengren, Anna LU ; Logan, Derek T. LU and Stålbrand, Henrik LU (2019) In Journal of Biological Chemistry 294(23). p.9100-9117
Abstract

The galactomannan utilization locus (BoManPUL) of the human gut bacterium Bacteroides ovatus encodes BoMan26B, a cell-surface– exposed endomannanase whose functional and structural features have been unclear. Our study now places BoMan26B in context with related enzymes and reveals the structural basis for its specificity. BoMan26B prefers longer substrates and is less restricted by galactose side-groups than the mannanase BoMan26A of the same locus. Using galactomannan, BoMan26B generated a mixture of (galactosyl) manno-oligosaccharides shorter than mannohexaose. Three defined manno-oligosaccharides had affinity for the SusD-like surface–exposed glycan-binding protein, predicted to be implicated in saccharide transport. Co-incubation... (More)

The galactomannan utilization locus (BoManPUL) of the human gut bacterium Bacteroides ovatus encodes BoMan26B, a cell-surface– exposed endomannanase whose functional and structural features have been unclear. Our study now places BoMan26B in context with related enzymes and reveals the structural basis for its specificity. BoMan26B prefers longer substrates and is less restricted by galactose side-groups than the mannanase BoMan26A of the same locus. Using galactomannan, BoMan26B generated a mixture of (galactosyl) manno-oligosaccharides shorter than mannohexaose. Three defined manno-oligosaccharides had affinity for the SusD-like surface–exposed glycan-binding protein, predicted to be implicated in saccharide transport. Co-incubation of BoMan26B and the periplasmic -galactosidase BoGal36A increased the rate of galactose release by about 10-fold compared with the rate without BoMan26B. The results suggested that BoMan26B performs the initial attack on galactomannan, generating oligosaccharides that after transport to the periplasm are processed by BoGal36A. A crystal structure of BoMan26B with galactosyl-mannotetraose bound in subsites 5 to 2 revealed an open and long active-site cleft with Trp-112 in subsite 5 concluded to be involved in mannosyl interaction. Moreover, Lys-149 in the 4 subsite interacted with the galactosyl side-group of the ligand. A phylogenetic tree consisting of GH26 enzymes revealed four strictly conserved GH26 residues and disclosed that BoMan26A and BoMan26B reside on two distinct phylogenetic branches (A and B). The three other branches contain lichenases, xylanases, or enzymes with unknown activities. Lys-149 is conserved in a narrow part of branch B, and Trp-112 is conserved in a wider group within branch B.

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published
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Journal of Biological Chemistry
volume
294
issue
23
pages
18 pages
publisher
ASBMB
external identifiers
  • scopus:85066942153
ISSN
0021-9258
DOI
10.1074/jbc.RA118.007171
language
English
LU publication?
yes
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1ff32802-07f2-4558-964e-dedeaf702d59
date added to LUP
2019-06-24 11:15:33
date last changed
2019-06-25 03:00:08
@article{1ff32802-07f2-4558-964e-dedeaf702d59,
  abstract     = {<p>The galactomannan utilization locus (BoManPUL) of the human gut bacterium Bacteroides ovatus encodes BoMan26B, a cell-surface– exposed endomannanase whose functional and structural features have been unclear. Our study now places BoMan26B in context with related enzymes and reveals the structural basis for its specificity. BoMan26B prefers longer substrates and is less restricted by galactose side-groups than the mannanase BoMan26A of the same locus. Using galactomannan, BoMan26B generated a mixture of (galactosyl) manno-oligosaccharides shorter than mannohexaose. Three defined manno-oligosaccharides had affinity for the SusD-like surface–exposed glycan-binding protein, predicted to be implicated in saccharide transport. Co-incubation of BoMan26B and the periplasmic -galactosidase BoGal36A increased the rate of galactose release by about 10-fold compared with the rate without BoMan26B. The results suggested that BoMan26B performs the initial attack on galactomannan, generating oligosaccharides that after transport to the periplasm are processed by BoGal36A. A crystal structure of BoMan26B with galactosyl-mannotetraose bound in subsites 5 to 2 revealed an open and long active-site cleft with Trp-112 in subsite 5 concluded to be involved in mannosyl interaction. Moreover, Lys-149 in the 4 subsite interacted with the galactosyl side-group of the ligand. A phylogenetic tree consisting of GH26 enzymes revealed four strictly conserved GH26 residues and disclosed that BoMan26A and BoMan26B reside on two distinct phylogenetic branches (A and B). The three other branches contain lichenases, xylanases, or enzymes with unknown activities. Lys-149 is conserved in a narrow part of branch B, and Trp-112 is conserved in a wider group within branch B.</p>},
  author       = {Bågenholm, Viktoria and Wiemann, Mathias and Reddy, Sumitha K. and Bhattacharya, Abhishek and Rosengren, Anna and Logan, Derek T. and Stålbrand, Henrik},
  issn         = {0021-9258},
  language     = {eng},
  number       = {23},
  pages        = {9100--9117},
  publisher    = {ASBMB},
  series       = {Journal of Biological Chemistry},
  title        = {A surface-exposed GH26 -mannanase from Bacteroides ovatus : Structure, role, and phylogenetic analysis of BoMan26B},
  url          = {http://dx.doi.org/10.1074/jbc.RA118.007171},
  volume       = {294},
  year         = {2019},
}