Discovery and Characterization of an Atypical Crustin Antimicrobial Peptide from .

Crustins are a family of antimicrobial peptides (AMPs) that play a pivotal role in the innate immune system of crustaceans. The discovery of novel AMPs from natural sources is crucial for expanding our current database of these peptides. Here, we identified and characterized a novel member of the crustin family, named Crus-SWD1, derived from . Crus-SWD1 consists of 138 amino acids and contains eight cysteine residues that form a conserved 'four-disulfide core' structure. Our recombinant Crus-SWD1 (rCrus-SWD1) exhibited potent inhibitory activity against three Gram-positive bacteria (, sp. T2, and ) and six Gram-negative bacteria (, , , , , and sp. L3), with minimum inhibitory concentrations ranging from 16 to 64 μM. Furthermore, rCrus-SWD1 demonstrated binding affinity towards both bacteria and pathogen-associated molecular patterns (PAMPs), and damaged bacterial barrier. Additionally, it effectively inhibited alkaline protease activity in and strains. These findings highlight the potential utility of this newly discovered crustin as an effective alternative to antibiotics.