The chitin-binding capability of Cy-AMP1 from cycad is essential to antifungal activity

Antimicrobial peptides are important components of the host innate immune responses by exerting broad‐spectrum microbicidal activity against pathogenic microbes. Cy‐AMP1 found in the cycad (Cycas revoluta) seeds has chitin‐binding ability, and the chitin‐binding domain was conserved in knottin‐type and hevein‐type antimicrobial peptides. The recombinant Cy‐AMP1 was expressed in Escherichia coli and purified to study the role of chitin‐binding domain. The mutants of Cy‐AMP1 lost chitin‐binding ability completely, and its antifungal activity was markedly decreased in comparison with native Cy‐AMP1. However, the antimicrobial activities of the mutant peptides are nearly identical to that of native one. It was suggested that the chitin‐binding domain plays an essential role in antifungal, but not antimicrobial, activity of Cy‐AMP1. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.