A new class (penaeidin class 4) of antimicrobial peptides from the Atlantic white shrimp (<i>Litopenaeus setiferus</i>) exhibits target specificity and an independent proline-rich-domain function

A highly pure, chemically defined representative of a new class of antimicrobial peptide from the Atlantic white shrimp (Litopenaeus setiferus), penaeidin class 4 [Pen4-1 (penaeidin class 4 isoform 1)], was produced synthetically. Chemical synthesis was achieved by native ligation from two separate domains yielding a bioactive peptide that reflected the characteristics of native penaeidin. Synthetic Pen4-1 proved to be an effective antimicrobial peptide, particularly against the broad-spectrum pathogen Fusarium oxysporum, exhibiting a complex effect on reproductive growth at inhibitory concentrations resulting in the suppression of spore formation. Pen4-1 exhibits unique features [not previously observed for penaeidins from the Pacific white shrimp (L. vannamei)], including target-species specificity against Gram-positive bacteria, indicating a potential partitioning of antimicrobial function among this family of peptides. The proline-rich domain of penaeidin class 4 alone was an active antimicrobial peptide, having the same target range as the full-length Pen4-1. These findings indicate that the proline-rich domain of penaeidin is sufficient to confer target specificity and that divergence in this domain between classes can result in a gain in antimicrobial function as observed for the proline-rich domain of Pen4-1.