CBM60 is a family of xylan-binding modules found in conjunction with xylanase enzymes in many bacterial species that attack plant cell walls. Xylan is the major hemicellulose component of most plant cell walls, and is one of the most complex carbohydrates targeted by CBMs. CBM60 modules are evolutionarily related to CBM36 domains as both show circular permutation in the beta-barrel folds. CBM60 targets xylan but is also able to bind cellulose and galactan and thus contribute towards breakdown of the plant cell wall. Recognition of the ligand is conferred primarily through the polar interactions of O2 (oxygen) and O3 of a single sugar with a protein-bound calcium ion [1].

1: Circular permutation provides an evolutionary link between two families of calcium-dependent carbohydrate binding modules. Montanier C, Flint JE, Bolam DN, Xie H, Liu Z, Rogowski A, Weiner DP, Ratnaparkhe S, Nurizzo D, Roberts SM, Turkenburg JP, Davies GJ, Gilbert HJ; J Biol Chem. 2010;285:31742-31754. PMID:20659893