title: Identification and glucan-binding properties of a new carbohydrate-binding module family.
abstract: The C-terminal 191-residue module of Cel5A from the alkalophilic Bacillus sp. 1139 comprises a carbohydrate-binding module (CBM) belonging to a previously unidentified family that we have classified as CBM family 28. This example, called CBM28, bound specifically to cello-oligosaccharides and mixed beta-(1,3)(1,4)-glucans (barley beta-glucan) with association constants of approximately (1-4)x10(4) M(-1). Its binding to barley beta-glucan was remarkably insensitive to pH between 7.0 and 10.9, in keeping with its alkalophilic source. CBM28 bound to cellulose having a significant non-crystalline content with an association constant similar to that for its binding to soluble glucans. CBM17 (CBM family 17) and CBM28 modules naturally occur as tandems. The CBM17/CBM28 tandem from Cel5A bound with apparent co-operativity to barley beta-glucan. The association of CBM28 with cello-oligosaccharides was driven enthalpically and marked by the different thermodynamic contribution of three putative binding subsites that accommodate a cellohexaose molecule.
authors.affiliation: The Protein Engineering Network of Centres of Excellence, PENCE Inc., National Business Centre, 750 Heritage Medical Research Centre, Edmonton, Alberta, Canada T6G 2S2. boraston@ysbl.york.ac.uk
authors.forename: Alisdair B
authors.initials: AB
authors.lastname: Boraston
authors.forename: Mazyar
authors.initials: M
authors.lastname: Ghaffari
authors.forename: R Antony J
authors.initials: RA
authors.lastname: Warren
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Kilburn
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005936:Glucans / Q000378:metabolism*; D008024:Ligands; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000378:metabolism; D011485:Protein Binding; D011956:Receptors, Cell Surface; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D005936:Glucans; D008024:Ligands; D009844:Oligosaccharides; D011956:Receptors, Cell Surface; C055213:saccharide-binding proteins