title: An unusual mode of galactose recognition by a family 32 carbohydrate-binding module.
abstract: Carbohydrate-binding modules (CBMs) are ancillary modules commonly associated with carbohydrate-active enzymes (CAZymes) that function to mediate the adherence of the parent enzyme to its carbohydrate substrates. CBM family 32 (CBM32) is one of the most diverse CBM families, whose members are commonly found in bacterial CAZymes that modify eukaryotic glycans. One such example is the putative μ-toxin, CpGH84A, of the family 84 glycoside hydrolases, which comprises an N-terminal putative β-N-acetylglucosaminidase catalytic module and four tandem CBM32s. Here, we report a unique mode of galactose recognition by the first CBM32, CBM32-1 from CpGH84A. Solution NMR-based analyses of CpGH84A CBM32-1 indicate a divergent subset of residues, located in ordered loops at the apex of the CBM, conferring specificity for the galacto-configured sugars galactose, GalNAc, and LacNAc that differs from those of the canonical galactose-binding CBM32s. This study showcases the impressive variability in ligand binding by this CBM family and offers insight into the growing role of these modules in the interaction of CAZymes with eukaryotic glycans.
authors: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
authors: Julie M
authors: JM
authors: Grondin
authors: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
authors: Seth
authors: S
authors: Chitayat
authors: Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, V8W 3P6, Canada.
authors: Elizabeth
authors: E
authors: Ficko-Blean
authors: Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, Ontario, M5G 1L7, Canada.
authors: Scott
authors: S
authors: Houliston
authors: Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, Ontario, M5G 1L7, Canada.
authors: Cheryl H
authors: CH
authors: Arrowsmith
authors: Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, V8W 3P6, Canada.
authors: Alisdair B
authors: AB
authors: Boraston
authors: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L 3N6, Canada; Protein Function Discovery Group, Queen's University, Kingston, Ontario, K7L 3N6, Canada. Electronic address: steven.smith@queensu.ca.
authors: Steven P
authors: SP
authors: Smith
mesh_terms: D000116:Acetylgalactosamine / Q000378:metabolism; D000595:Amino Acid Sequence; D000606:Amino Sugars / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D003016:Clostridium perfringens / Q000201:enzymology; D005690:Galactose / Q000378:metabolism*; D006821:Hyaluronoglucosaminidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D013379:Substrate Specificity
chemical_list: D000606:Amino Sugars; D001426:Bacterial Proteins; C000458:N-acetyllactosamine; D006821:Hyaluronoglucosaminidase; D000116:Acetylgalactosamine; D005690:Galactose
keywords: 2D; CAZyme; CBM; Clostridium perfringens; HSQC; NMR spectroscopy; NOE; NOE spectroscopy; NOESY; STD; carbohydrate-active enzyme; carbohydrate-binding module; family 84 glycoside hydrolase; galacto-configured sugar; heteronuclear single quantum coherence; nuclear Overhauser enhancement; saturation transfer difference; two-dimensional