Molecular cloning and characterization of a cDNA encoding cellobiose dehydrogenase from the wood-rotting fungus Grifola frondosa.

Cloning of a cDNA encoding cellobiose dehydrogenase (CDH) from the wood-rotting fungus Grifola frondosa, which produces the edible maitake mushroom, was performed using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends. The CDH cDNA consisted of 2469 bp, including an open reading frame encoding the 18-amino acid signal peptide at the N-terminal region and the 750-amino acid mature protein with a predicted molecular mass of 79.6 kDa and a pI value of 4.32. Analysis of the amino acid sequence revealed that it contains a flavin-binding motif, two glucose-methanol-choline oxidoreductase motifs, and two possible residues for heme ligand binding (Met61 and His58). The amino acid sequence of G. frondosa CDH (GfrCDH) has a high degree of identity with three known CDHs from basidiomycetes, but not with two CDHs from ascomycetes. In addition, transcription of the CDH gene in G. frondosa grown on several carbon sources was analyzed by RT-PCR. mRNA of GfrCDH was detected from mycelia grown on cellobiose and cellulose, but not on glucose. Consequently, transcription of the GfrCDH gene seems to be promoted under conditions favoring cellulose degradation, and to be regulated by carbon catabolite repression.