Docking and Molecular Dynamics Study of the Carbohydrate Binding Module from Trichoderma reesei Cel7A on the Surfaces of the Cellulose Ⅲ_(1) Crystal

We report the systematic survey of the binding free energies at the interface between a carbohydrate binding module(CBM)of Cel7A and the celluloseⅢ_(1)crystal model using grid docking searches and molecular dynamics simulations.The two hydrophobic crystal surfaces were involved in the distinct energy minima of the binding free energy.The complex models,each with the CBM at the minimum energy position,stably formed in the solution state.The binding free energies of the celluloseⅢ_(1)complex models,based on both static and dynamics states,were comparable to those of the native cellulose complex models.However,the celluloseⅢ_(1)crystal had a larger binding surface,which is compatible with the observed high enzymatic activity of Cel7A for the celluloseⅢ_(1)substrate.

Redesigning transcription factor Cre1 for alleviating carbon catabolite repression in Trichoderma reesei

Carbon catabolite repression(CCR),which is mainly mediated by Cre1 and triggered by glucose,leads to a decrease in cellulase production in Trichoderma reesei.Many studies have focused on modifying Cre1 for alleviating CCR.Based on the homologous alignment of CreA from wild-type Penicillium oxalicum 114–2(Po-0)and cellulase hyperproducer JUA10-1(Po-1),we constructed a C-terminus substitution strain—Po-2—with decreased transcriptional levels of cellulase and enhanced CCR.Results revealed that the C-terminal domain of CreAPo−1 plays an important role in alleviating CCR.Furthermore,we replaced the C-terminus of Cre1 with that of CreAPo−1 in T.reesei(Tr-0)and generated Tr-1.As a control,the C-terminus of Cre1 was truncated and Tr-2 was generated.The transcriptional profiles of these transformants revealed that the C-terminal chimera greatly improves cellulase transcription in the presence of glucose and thus upregulates cellulase in the presence of glucose and weakens CCR,consistent with truncating the C-terminus of Cre1 in Tr-0.Therefore,we propose constructing a C-terminal chimera as a new strategy to improve cellulase production and alleviate CCR in the presence of glucose.