Cloning and functional identification of C-4 methyl sterol oxidase genes from the penicillin-producing fungus Penicillium chrysogenum.

Two C-4 methyl sterol oxidase genes (Pcerg25A and Pcerg25B) that are involved in ergosterol biosynthesis have been cloned from the penicillin-producing fungus Penicillium chrysogenum. cDNAs of both Pcerg25A and Pcerg25B have an ORF 885 bp in length, encoding a peptide of 295 residues. The deduced amino acid sequences of PcErg25A and PcErg25B show 86% identity, and have high identities to the characterized C-4 methyl sterol oxidases from Candida albicans and Saccharomyces cerevisiae. The function of Pcerg25A and Pcerg25B was identified by complementation of a yeast erg25-deficient strain. Pcerg25A is located in the DNA region containing the penicillin gene cluster, and thus its copy number is dependent on the patterns of the cluster region. Up to eight copies of Pcerg25A were found in the high-productivity strain NCPC 10086. By contrast, Pcerg25B was present in just a single copy in all tested P. chrysogenum genomes. Differences in the transcript level of either Pcerg25A or Pcerg25B were observed in different P. chrysogenum strains by real-time quantitative reverse transcriptase PCR analysis.