title: Mechanisms involved in xyloglucan catabolism by the cellulosome-producing bacterium Ruminiclostridium cellulolyticum.
abstract: Xyloglucan, a ubiquitous highly branched plant polysaccharide, was found to be rapidly degraded and metabolized by the cellulosome-producing bacterium Ruminiclostridium cellulolyticum. Our study shows that at least four cellulosomal enzymes displaying either endo- or exoxyloglucanase activities, achieve the extracellular degradation of xyloglucan into 4-glucosyl backbone xyloglucan oligosaccharides. The released oligosaccharides (composed of up to 9 monosaccharides) are subsequently imported by a highly specific ATP-binding cassette transporter (ABC-transporter), the expression of the corresponding genes being strongly induced by xyloglucan. This polysaccharide also triggers the synthesis of cytoplasmic β-galactosidase, α-xylosidase, and β-glucosidase that act sequentially to convert the imported oligosaccharides into galactose, xylose, glucose and unexpectedly cellobiose. Thus R. cellulolyticum has developed an energy-saving strategy to metabolize this hemicellulosic polysaccharide that relies on the action of the extracellular cellulosomes, a highly specialized ABC-transporter, and cytoplasmic enzymes acting in a specific order. This strategy appears to be widespread among cellulosome-producing mesophilic bacteria which display highly similar gene clusters encoding the cytosolic enzymes and the ABC-transporter.
authors.affiliation: Aix-Marseille Université-CNRS, Laboratoire de Chimie Bactérienne, UMR7283, IMM, 31 chemin Joseph Aiguier, F-13402 Marseille, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Ravachol
authors.affiliation: Aix-Marseille Université-CNRS, Laboratoire de Chimie Bactérienne, UMR7283, IMM, 31 chemin Joseph Aiguier, F-13402 Marseille, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: de Philip
authors.affiliation: Aix-Marseille Université-CNRS, Laboratoire de Chimie Bactérienne, UMR7283, IMM, 31 chemin Joseph Aiguier, F-13402 Marseille, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Borne
authors.affiliation: Plate-forme de Protéomique, IMM, 31 chemin Joseph Aiguier, F-13402 Marseille, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Mansuelle
authors.affiliation: Aix-Marseille Université-CNRS, Laboratoire d'Architecture et Fonction des Macromolécules Biologiques, UMR7257, Parc Technologique de Luminy, F-13288 Marseille, France.
authors.forename: María J
authors.initials: MJ
authors.lastname: Maté
authors.affiliation: Aix-Marseille Université-CNRS, Laboratoire de Chimie Bactérienne, UMR7283, IMM, 31 chemin Joseph Aiguier, F-13402 Marseille, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Perret
authors.affiliation: Aix-Marseille Université-CNRS, Laboratoire de Chimie Bactérienne, UMR7283, IMM, 31 chemin Joseph Aiguier, F-13402 Marseille, France.
authors.forename: Henri-Pierre
authors.initials: HP
authors.lastname: Fierobe
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D044602:Cellulases / Q000378:metabolism; D044603:Cellulosomes / Q000378:metabolism*; D000068016:Eubacteriales / Q000378:metabolism*; D003593:Cytoplasm / Q000201:enzymology; D005936:Glucans / Q000378:metabolism*; D013379:Substrate Specificity; D014990:Xylans / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D005936:Glucans; D014990:Xylans; C029353:xyloglucan; D044602:Cellulases