Comparison of the structural changes in two cellobiohydrolases, CcCel6A and CcCel6C, from Coprinopsis cinerea - a tweezer-like motion in the structure of CcCel6C

摘要: The basidiomycete Coprinopsis cinerea produces five cellobiohydrolases belonging to glycoside hydrolase family 6 (GH6). Among these enzymes, C. cellulase 6C (CcCel6C), but not 6A (CcCel6A), can efficiently hydrolyze carboxymethyl cellulose and is constitutively expressed in cinerea. In contrast, CcCel6A possesses a cellulose-binding domain, strongly induced by cellobiose. Here, we determined the crystal structures of catalytic domain complexed with Hepes buffer molecule, cellobiose, p-nitrophenyl β-D-cellotrioside (pNPG3). A notable feature GH6 that active site enclosed two loops form tunnel, have been demonstrated open close response ligand binding. tunnel CcCel6A-Hepes seen as form, whereas tunnels CcCel6A-cellobiose CcCel6A-pNPG3 adopt closed form. pNPG3 was hydrolyzed CcCel6A, bound subsites +1 +4. On basis this observation, constructed mutants, D164A CcCel6C D102A. Neither nor D102A phosphoric acid-swollen cellulose. We previously unbound complex ligand, both which present study, mutants were identified However, motion angle more than 10-fold greater CcCel6A. width cleft narrowed, owing tweezer-like motion.