The cellulose-binding domain of cellobiohydrolase Cel7A from Trichoderma reesei is also a thermostabilizing domain

The thermostability of cellobiohydrolase I Cel7A from Trichoderma reesei was investigated using dynamic light scattering. While the whole enzyme displayed a melting point of 59 degrees C, the catalytic domain obtained via papain-catalyzed proteolysis was shown to denature at 51 degrees C and the cellulose-binding domain (with linker attached) melted at 65-66 degrees C. This variation in individual melting temperatures is proposed to account for the full retention of binding capacity of Cel7A at 50 degrees C, along with a loss of catalytic activity observed for the catalytic domain alone. Thus, the cellulose-binding domain of Cel7A acts as a thermostabilizing domain for the enzyme. The effect of reducing agents on the protein melting behavior was also investigated. (C) 2011 Elsevier B.V. All rights reserved.