Structural and Gene Characterization of a New Antifungal Peptide Obtained from Penicillium crustosum FP11 Strain

A novel antifungal peptide, PcAFP (6.48 kDa, pI 8.83), was obtained from the culture supernatant of the fungus Penicillium crustosum. The gene encoding the PcAFP peptide was isolated based on its homologue in Penicillium chrysogenum, PgAFP. PcAFP is a small, cystine-rich peptide, and the mature peptide consists of 58 amino acid residues. The immature P. crustosum antifungal protein (AFP) showed 95.65% identity to the antifungal protein of P. chrysogenum, while the mature peptide showed 98.28% identity with PgAFP. Molecular modeling of the tertiary structure of the mature peptide revealed details of the conserved structure of the AFPs, such as the β-barrel motif stabilized by three disulfide bonds and the l-core motif. Analysis of the extract by 16% tricine SDS-PAGE showed a 6.9 kDa peptide, which was close to the predicted molecular mass of the mature peptide of 6.48 kDa. Assays of antimicrobial activity, performed by broth microdilution using the crude extract obtained from the culture medium, showed activity against Candida albicans. These results demonstrate the conservation of the PcAPF gene and the high level of identity with the PgAFP antifungal protein of P. chrysogenum. Given these structural and biochemical characteristics, PcAFP could be a potential candidate for future investigations that may aid in the development of new antifungal compounds.