Gene sequence and analysis of protein domains of EGB, a novel family E endoglucanase from Fibrobacter succinogenes S85

Abstract

The endoglucanase gene (endB) of Fibrobacter succinogenes S85 encodes a protein of 555 amino acids (EGB) with a M(r) of 62,500. EGB shows homology with cellulases belonging to family E. Residues involved in the catalytic activity of CelD from Clostridium thermocellum are also found in EGB. Structure predictions suggest that EGB, like CelD, comprises a large alpha-helical catalytic domain plus a beta-strand domain of unknown function located in the N-terminal part of the protein. Construction of a phylogenetic tree of family E catalytic domains revealed that EGB is closest to a cellodextrinase from Butyrivibrio fibrisolvens.