Structure and ligand binding of carbohydrate-binding module CsCBM6-3 reveals similarities with fucose-specific lectins and "galactose-binding" domains

TY - JOUR

T1 - Structure and ligand binding of carbohydrate-binding module CsCBM6-3 reveals similarities with fucose-specific lectins and "galactose-binding" domains

AU - Boraston, A B

AU - Notenboom, V

AU - Warren, R A J

AU - Kilburn, D G

AU - Rose, D R

AU - Davies, G

PY - 2003/3/28

Y1 - 2003/3/28

N2 - Carbohydrate-binding polypeptides, including carbohydrate-binding modules (CBMs) from polysaccharidases, and lectins, are widespread in nature. Whilst CBMs are classically considered distinct from lectins, in that they are found appended to polysaccharide-degrading enzymes, this distinction is blurring. The crystal structure of CsCBM6-3, a "sequence-family 6" CBM in a xylanase from Clostridium stercorarium, at 2.3 Angstrom reveals a similar, all beta-sheet fold to that from MvX56, a module found in a family 33 glycoside hydrolase sialidase from Micromonospora viridifaciens, and the lectin AAA from Anguilla anguilla. Sequence analysis leads to the classification of MvX56 and AAA into a family distinct from that containing CsCBM6-3. Whilst these polypeptides are similar in structure they have quite different carbohydrate-binding specificities. AAA is known to bind fucose; CsCBM6-3 binds cellulose, xylan and other beta-glucans. Here we demonstrate that MvX56 binds galactose, lactose and sialic acid. Crystal structures of CsCBM6-3 in complex with xylotriose, cellobiose, and laminaribiose, 2.0 Angstrom, 1.35 Angstrom, and 1.0 Angstrom resolution, respectively, reveal that the binding site of CsCBM6-3 resides on the same polypeptide face as for MvX56 and AAA. Subtle differences in the ligand-binding surface give rise to the different specificities and biological activities, further blurring the distinction between classical lectins and CBMs. (C) 2003 Elsevier Science Ltd. All rights reserved.

AB - Carbohydrate-binding polypeptides, including carbohydrate-binding modules (CBMs) from polysaccharidases, and lectins, are widespread in nature. Whilst CBMs are classically considered distinct from lectins, in that they are found appended to polysaccharide-degrading enzymes, this distinction is blurring. The crystal structure of CsCBM6-3, a "sequence-family 6" CBM in a xylanase from Clostridium stercorarium, at 2.3 Angstrom reveals a similar, all beta-sheet fold to that from MvX56, a module found in a family 33 glycoside hydrolase sialidase from Micromonospora viridifaciens, and the lectin AAA from Anguilla anguilla. Sequence analysis leads to the classification of MvX56 and AAA into a family distinct from that containing CsCBM6-3. Whilst these polypeptides are similar in structure they have quite different carbohydrate-binding specificities. AAA is known to bind fucose; CsCBM6-3 binds cellulose, xylan and other beta-glucans. Here we demonstrate that MvX56 binds galactose, lactose and sialic acid. Crystal structures of CsCBM6-3 in complex with xylotriose, cellobiose, and laminaribiose, 2.0 Angstrom, 1.35 Angstrom, and 1.0 Angstrom resolution, respectively, reveal that the binding site of CsCBM6-3 resides on the same polypeptide face as for MvX56 and AAA. Subtle differences in the ligand-binding surface give rise to the different specificities and biological activities, further blurring the distinction between classical lectins and CBMs. (C) 2003 Elsevier Science Ltd. All rights reserved.

KW - carbohydrate-binding module

KW - cellulose

KW - xylan

KW - lectin

KW - cellulose-binding domain

KW - LIVIDANS XYLANASE 10A

KW - CRYSTAL-STRUCTURES

KW - MACROMOLECULAR STRUCTURES

KW - GLYCOSIDE HYDROLASES

KW - PROTEIN-STRUCTURE

KW - RECOGNITION

KW - FAMILY

KW - GLYCOSYLTRANSFERASES

KW - COEFFICIENTS

KW - REFINEMENT

U2 - 10.1016/S0022-2836(03)00152-9

DO - 10.1016/S0022-2836(03)00152-9

M3 - Article

SN - 0022-2836

VL - 327

SP - 659

EP - 669

JO - Journal of Molecular Biology

JF - Journal of Molecular Biology

IS - 3

ER -