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A complex gene locus enables xyloglucan utilization in the model saprophyte Cellvibrio japonicus.

Larsbrink J, Thompson AJ, Lundqvist M, Gardner JG, Davies GJ, Brumer H - Mol. Microbiol. (2014)

Bottom Line: Here, we present the identification and molecular characterization of a complex genetic locus that is required for xyloglucan utilization by the model saprophyte Cellvibrio japonicus.In harness, transcriptomics, reverse genetics, enzyme kinetics, and structural biology indicate that the encoded cohort of an α-xylosidase, a β-galactosidase, and an α-l-fucosidase is specifically adapted for efficient, concerted saccharification of dicot (fucogalacto)xyloglucan oligosaccharides following import into the periplasm via an associated TonB-dependent receptor.The data support a biological model of xyloglucan degradation by C. japonicus with striking similarities - and notable differences - to the complex polysaccharide utilization loci of the Bacteroidetes.

View Article: PubMed Central - PubMed

Affiliation: Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Centre, 106 91, Stockholm, Sweden.

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Proposed pathway of (fucogalacto)xyloglucan degradation by C. japonicus. Sugar symbols are as follows: Glc – blue circles, Xyl – orange stars, Gal – yellow circles, Fuc – red pentagons. Secreted enzymes with endo-xyloglucanase activity depolymerize the polysaccharides into xyloglucan oligosaccharides which are imported into the periplasm by the TonB-dependent receptor of the locus. In the periplasm, CjBgl35A and CjAfc95A strip off galactose and fucose from the oligosaccharides respectively. In concert, CjXyl31A and an unknown β-glucosidase cleave off terminal xylose and glucose residues from the non-reducing end in an iterative manner.
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fig06: Proposed pathway of (fucogalacto)xyloglucan degradation by C. japonicus. Sugar symbols are as follows: Glc – blue circles, Xyl – orange stars, Gal – yellow circles, Fuc – red pentagons. Secreted enzymes with endo-xyloglucanase activity depolymerize the polysaccharides into xyloglucan oligosaccharides which are imported into the periplasm by the TonB-dependent receptor of the locus. In the periplasm, CjBgl35A and CjAfc95A strip off galactose and fucose from the oligosaccharides respectively. In concert, CjXyl31A and an unknown β-glucosidase cleave off terminal xylose and glucose residues from the non-reducing end in an iterative manner.

Mentions: Transcript and reverse genetics analyses allow us to conclude that xyl31A, bgl35A, tbdr, and afc95A (Fig. 1) constitute a xyloglucan utilization locus (XyGUL), which is the primary genetic determinant conferring C. japonicus with the ability to saccharify this ubiquitous plant cell wall polysaccharide. Together with substrate specificity and structural analysis of the encoded glycoside hydrolases, subcellular localization data allow us to propose an updated model of XyG degradation in C. japonicus (Fig. 6). In this model, XyG polysaccharide is hydrolysed into component oligosaccharides by one or more endo-xyloglucanase(s). The liberated XyGOs are then imported into the periplasm via the TBDR (Ferguson and Deisenhofer, 2002; Koebnik, 2005; Dejean et al., 2013), where the exo-glycosidases CjXyl31A, CjBgl35A, and CjAfc95A work in concert, together with a currently unidentified β-glucosidase(s), to yield monosaccharides for further catabolism.


A complex gene locus enables xyloglucan utilization in the model saprophyte Cellvibrio japonicus.

Larsbrink J, Thompson AJ, Lundqvist M, Gardner JG, Davies GJ, Brumer H - Mol. Microbiol. (2014)

Proposed pathway of (fucogalacto)xyloglucan degradation by C. japonicus. Sugar symbols are as follows: Glc – blue circles, Xyl – orange stars, Gal – yellow circles, Fuc – red pentagons. Secreted enzymes with endo-xyloglucanase activity depolymerize the polysaccharides into xyloglucan oligosaccharides which are imported into the periplasm by the TonB-dependent receptor of the locus. In the periplasm, CjBgl35A and CjAfc95A strip off galactose and fucose from the oligosaccharides respectively. In concert, CjXyl31A and an unknown β-glucosidase cleave off terminal xylose and glucose residues from the non-reducing end in an iterative manner.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4285296&req=5

fig06: Proposed pathway of (fucogalacto)xyloglucan degradation by C. japonicus. Sugar symbols are as follows: Glc – blue circles, Xyl – orange stars, Gal – yellow circles, Fuc – red pentagons. Secreted enzymes with endo-xyloglucanase activity depolymerize the polysaccharides into xyloglucan oligosaccharides which are imported into the periplasm by the TonB-dependent receptor of the locus. In the periplasm, CjBgl35A and CjAfc95A strip off galactose and fucose from the oligosaccharides respectively. In concert, CjXyl31A and an unknown β-glucosidase cleave off terminal xylose and glucose residues from the non-reducing end in an iterative manner.
Mentions: Transcript and reverse genetics analyses allow us to conclude that xyl31A, bgl35A, tbdr, and afc95A (Fig. 1) constitute a xyloglucan utilization locus (XyGUL), which is the primary genetic determinant conferring C. japonicus with the ability to saccharify this ubiquitous plant cell wall polysaccharide. Together with substrate specificity and structural analysis of the encoded glycoside hydrolases, subcellular localization data allow us to propose an updated model of XyG degradation in C. japonicus (Fig. 6). In this model, XyG polysaccharide is hydrolysed into component oligosaccharides by one or more endo-xyloglucanase(s). The liberated XyGOs are then imported into the periplasm via the TBDR (Ferguson and Deisenhofer, 2002; Koebnik, 2005; Dejean et al., 2013), where the exo-glycosidases CjXyl31A, CjBgl35A, and CjAfc95A work in concert, together with a currently unidentified β-glucosidase(s), to yield monosaccharides for further catabolism.

Bottom Line: Here, we present the identification and molecular characterization of a complex genetic locus that is required for xyloglucan utilization by the model saprophyte Cellvibrio japonicus.In harness, transcriptomics, reverse genetics, enzyme kinetics, and structural biology indicate that the encoded cohort of an α-xylosidase, a β-galactosidase, and an α-l-fucosidase is specifically adapted for efficient, concerted saccharification of dicot (fucogalacto)xyloglucan oligosaccharides following import into the periplasm via an associated TonB-dependent receptor.The data support a biological model of xyloglucan degradation by C. japonicus with striking similarities - and notable differences - to the complex polysaccharide utilization loci of the Bacteroidetes.

View Article: PubMed Central - PubMed

Affiliation: Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Centre, 106 91, Stockholm, Sweden.

Show MeSH