The Location of the Ligand-binding Site of Carbohydrate-binding Modules That Have Evolved from a Common Sequence Is Not Conserved
Abstract
Polysaccharide-degrading enzymes are generally modular proteins that contain non-catalytic carbohydrate-binding modules (CBMs), which potentiate the activity of the catalytic module. CBMs have been grouped into sequence-based families, and three-dimensional structural data are available for half of these families. Clostridium thermocellum xylanase 11A is a modular enzyme that contains a CBM from family 6 (CBM6), for which no structural data are available. We have determined the crystal structure of this module to a resolution of 2.1 A. The protein is a beta-sandwich that contains two potential ligand-binding clefts designated cleft A and B. The CBM interacts primarily with xylan, and NMR spectroscopy coupled with site-directed mutagenesis identified cleft A, containing Trp-92, Tyr-34, and Asn-120, as the ligand-binding site. The overall fold of CBM6 is similar to proteins in CBM families 4 and 22, although surprisingly the ligand-binding site in CBM4 and CBM22 is equivalent to cleft B in CBM6. These structural data define a superfamily of CBMs, comprising CBM4, CBM6, and CBM22, and demonstrate that, although CBMs have evolved from a relatively small number of ancestors, the structural elements involved in ligand recognition have been assembled at different locations on the ancestral scaffold.
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BibTeX
@article{czjzek2026location,
title = {{The Location of the Ligand-binding Site of Carbohydrate-binding Modules That Have Evolved from a Common Sequence Is Not Conserved}},
author = {Mirjam Czjzek and David Bolam and Amor Mosbah and Julie Allouch and Carlos M.G.A. Fontes and Luis M.A. Ferreira and Olivier Bornet and Véronique Zamboni and Hervé Darbon and Nicola Smith and Gary Black and Bernard Henrissat and Harry Gilbert},
journal = {Journal of Biological Chemistry},
year = {2026},
month = oct,
doi = {10.1074/jbc.m109142200},
url = {https://hal.science/hal-05797422v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - The Location of the Ligand-binding Site of Carbohydrate-binding Modules That Have Evolved from a Common Sequence Is Not Conserved
AU - Mirjam Czjzek
AU - David Bolam
AU - Amor Mosbah
AU - Julie Allouch
AU - Carlos M.G.A. Fontes
AU - Luis M.A. Ferreira
AU - Olivier Bornet
AU - Véronique Zamboni
AU - Hervé Darbon
AU - Nicola Smith
AU - Gary Black
AU - Bernard Henrissat
AU - Harry Gilbert
PY - 2026
DA - 2026/10/13
JO - Journal of Biological Chemistry
DO - 10.1074/jbc.m109142200
UR - https://hal.science/hal-05797422v1
AB - Polysaccharide-degrading enzymes are generally modular proteins that contain non-catalytic carbohydrate-binding modules (CBMs), which potentiate the activity of the catalytic module. CBMs have been grouped into sequence-based families, and three-dimensional structural data are available for half of these families. Clostridium thermocellum xylanase 11A is a modular enzyme that contains a CBM from family 6 (CBM6), for which no structural data are available. We have determined the crystal structure of this module to a resolution of 2.1 A. The protein is a beta-sandwich that contains two potential ligand-binding clefts designated cleft A and B. The CBM interacts primarily with xylan, and NMR spectroscopy coupled with site-directed mutagenesis identified cleft A, containing Trp-92, Tyr-34, and Asn-120, as the ligand-binding site. The overall fold of CBM6 is similar to proteins in CBM families 4 and 22, although surprisingly the ligand-binding site in CBM4 and CBM22 is equivalent to cleft B in CBM6. These structural data define a superfamily of CBMs, comprising CBM4, CBM6, and CBM22, and demonstrate that, although CBMs have evolved from a relatively small number of ancestors, the structural elements involved in ligand recognition have been assembled at different locations on the ancestral scaffold.
SN - 0021-9258
SN - 1083-351X
ER -