Fig. 5

Structural comparison of four different catalytic clefts from glycoside hydrolase GH9 cellulases. The figure depicts cellobiohydrolase Cbh9A (PDB structure 1RQ5), processive endoglucanase pEG2 (Cel9D, PDB 1CLC), pEG4 (Cel9F, predicted structure), and non-processive endoglucanase Cel9T (PDB accession 2YIK) as gray surface plots and their corresponding sugar-binding moieties (red sticks) and catalytic triad (in blue). Cellohexaose (Glc₆) was taken from PDB 7CEL. Numbers in black depict cello-oligosaccharide positions (+ 2 to − 2) according to the nomenclature for sugar-binding subsites [61] in the catalytic cleft from protein–ligand interaction data for Cbh9A according to [56], Cel9T [57], Cel9A from T. fusca [59] and the structural sequence alignment (Fig. 4)