Cloning, sequencing, and heterologous expression of a cellulase-encoding cDNA (cbh1) from Penicillium janthinellum

From a Penicillium janthinellum cDNA library, two clones with 1.8- and 1.9-kb inserts were isolated by hybridization to a Trichoderma reesei cellulase-encoding gene probe (egl1). Both cDNAs have identical 5' ends and coding sequences, but different polyadenylation start points in their 3' untranslated regions. In the nucleotide (nt) sequence, one open reading frame of 537 amino acids was detected which shows 56% homology with endoglucanase I of T. reesei and 70% homology with cellobiohydrolase I of T. reesei, Phanerochaete chrysosporium, and Humicola grisea. Expression of the 1.9-kb cDNA in the Escherichia coli T7 system led to the detection of a 57-kDa protein, in agreement with the theoretical value. Fusion to the promoter of the yeast phosphoglycerokinase-encoding gene led to efficient expression and partial secretion of the cDNA-encoded cellulase with cellobiohydrolase I activity in Saccharomyces cerevisiae.