Family 6 carbohydrate-binding modules display multiple beta1,3-linked glucan-specific binding interfaces.

Márcia A S Correia, Virgínia M R Pires, Harry J Gilbert, David N Bolam, Vânia O Fernandes, Victor D Alves, José A M Prates, Luís M A Ferreira, Carlos M G A Fontes

FEMS microbiology letters 2009 Nov

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Noncatalytic carbohydrate-binding modules (CBMs), which are found in a variety of carbohydrate-degrading enzymes, have been grouped into sequence-based families. CBMs, by recruiting their appended enzymes onto the surface of the target substrate, potentiate catalysis particularly against insoluble substrates. Family 6 CBMs (CBM6s) display unusual properties in that they present two potential ligand-binding sites termed clefts A and B, respectively. Cleft B is located on the concave surface of the beta-sandwich fold while cleft A, the more common binding site, is formed by the loops that connect the inner and the outer beta-sheets. Here, we report the biochemical properties of CBM6-1 from Cellvibrio mixtus CmCel5A. The data reveal that CBM6-1 specifically recognizes beta1,3-glucans through residues located both in cleft A and in cleft B. In contrast, a previous report showed that a CBM6 derived from a Bacillus halodurans laminarinase binds to beta1,3-glucans only in cleft A. These studies reveal a different mechanism by which a highly conserved protein platform can recognize beta1,3-glucans.

Citation

Márcia A S Correia, Virgínia M R Pires, Harry J Gilbert, David N Bolam, Vânia O Fernandes, Victor D Alves, José A M Prates, Luís M A Ferreira, Carlos M G A Fontes. Family 6 carbohydrate-binding modules display multiple beta1,3-linked glucan-specific binding interfaces. FEMS microbiology letters. 2009 Nov;300(1):48-57