Crystal structure of a glycoside hydrolase family 6 enzyme, CcCel6C, a cellulase constitutively produced by Coprinopsis cinerea

Abstract

The basidiomycete Coprinopsis cinerea produces the glycoside hydrolase family 6 enzyme CcCel6C at low and constitutive levels. CcCel6C exhibits unusual cellobiohydrolase activity; it hydrolyses carboxymethyl cellulose, which is a poor substrate for typical cellobiohydrolases. Here, we determined the crystal structures of CcCel6C unbound and in complex with p‐nitrophenyl β‐d‐cellotrioside and cellobiose. CcCel6C consists of a distorted seven‐stranded β/α barrel and has an enclosed tunnel, which is observed in other cellobiohydrolases from ascomecetes Hypocrea jecorina (HjeCel6A) and Humicola insolens (HinCel6A). In HjeCel6A and HinCel6A, ligand binding produces a conformational change that narrows this tunnel. In contrast, the tunnel remains wide in CcCel6C and the conformational change appears to be less favourable than in HjeCel6A and HinCel6A. The ligand binding cleft for subsite −3 of CcCel6C is also wide and is rather similar to that of endoglucanase. These results suggest that the open tunnel and the wide cleft are suitable for the hydrolysis of carboxymethyl cellulose.

Fungal Cellulases

“…670 The authors suggested the structure was an additional example of a GH6 CBH based on prior characterization on PASC despite the high sequence homology with the H. insolens EG Cel6B. However, in the current study, CcCel6C was tested for activity on CMC and demonstrated specificity for the substrate unlike any other GH6 CBH.…”

Effects of Tyr555 and Trp678 on the processivity of cellobiohydrolase A from Ruminiclostridium thermocellum: A simulation study

“…Cellulose is a polysaccharide formed by the polymerization of several hundreds to thousands of β‐(1,4)‐ d ‐glucose units. Moreover, cellulose is a predominant component of the plant cell wall . Native celluloses are insoluble materials that can be degraded into small cellodextrin or glucose by glycoside hydrolases (GHs) .…”

Crystal structure of the N‐terminal domain of a glycoside hydrolase family 131 protein from Coprinopsis cinerea

“…The entire genomic sequence of C. cinerea has been reported [2]. The fungal genome contains many genes coding for enzymes that participate in plant cell biomass degradation, and we have previously reported the crystal structures of cellobiohydrolases [3][4][5]. C. cinerea possesses a gene, CC1G_07166, which encodes a protein homologous to PaGluc131A (42% identity).…”