Cloning and characterization of a new exo-cellulase gene, cel3, in Irpex lacteus

A new cellulose-inducible gene (named cel3) was isolated from a strain of t he white rot basidiomycete, Irpex lacteus MC-2. The cel3 open reading frame , containing two introns, encodes a polypeptide of 526 amino acids residues with a molecular mass of 55 794 Da. Expression of the cel3 gene was induce d by various insoluble celluloses and CM-cellulose. Transcription of cel3 w as abolished when cells were cultivated in media containing the above cellu losic substrates, but added with glucose, fructose or lactose, while additi on of glycerol or mannitol did not affect the cel3 mRNA level. The amino ac id sequence of the catalytic domain of the Cel3 protein was homologous to t hat of fungal exo-type cellulases belonging to family 7 of the glycosyl hyd rolases. A phylogenetic study showed that these exo-type cellulases can be clearly separated from family 7 endo-type cellulases. (C) 1999 Federation o f European Microbiological Societies. Published by Elsevier Science B.V. Al l rights reserved.