Using a reverse-transcription polymerase chain reaction (RT-PCR) technique, cytochrome 1,3450 genes were cloned from the lignin-degrading basidiomycete, Coriolus versicolor. One possible P450 gene was identified, which consisted of 1,672 nucleotides and a poly(A) tail and encoded a deduced protein containing 449 amino acids. The deduced amino acid sequence revealed the presence of the P450 heme-binding motif, strongly suggesting that this protein belongs to the P450 superfamily, then designated CYP512A1. The deduced protein showed sequential similarity to other known P450s from several micro-organisms, such as Aspergillus terreus, Gibberella fujikuroi, and Neurospora crassa, with 30-35% identity. Since the identity of the amino acid sequence was less than 40% with any other P450s, this protein was suggested to be the first member of a new family of cytochrome P450. In addition, a differential display RT-PCR analysis showed the expression of the other P450 genes, which were up-regulated by the addition of dibenzothiophene and 4-methyldibenzothiophene-5-oxide. Using the 5' rapid amplification of cDNA ends method, a 520-nucleotide sequence, including the P450 motif-coding region, was determined for one clone. The deduced protein showed high similarity to CYP512A1 but less than 40% identity with P450s from other organisms. A chemical stress-responsive expression of P450 is suggested for the first time in basidiomycetes.