Figure 5.

Structure of proteins homologous to expansin domains. (a) Expansin domain 1 (the catalytic domain of a GH45 endoglucanase from Humicola insolens; Protein Data Bank (PDB) code 2ENG). (b) Expansin domain 2 (a G2A protein from Phleum pratense; PDB 1WHO). In (a), the domain forms a β barrel; amino-acid residues that are conserved in expansins are indicated in the single-letter amino-acid code.