Stylicins, a new family of antimicrobial peptides from the Pacific blue shrimp Litopenaeus stylirostris

The present study reports the characterization of Ls-Stylicin1, a novel antimicrobial peptide from the penaeid shrimp, Litopenaeus stylirostris. The predicted mature peptide of 82 residues is negatively charged (theoretical pI = 5.0) and characterized by a proline-rich N-terminal region and a C-terminal region containing 13 cysteine residues. The recombinant Ls-Stylicin1 has been isolated in both monomeric and dimeric forms. Both display strong antifungal activity against Fusarium oxysporum (1.25 μM < MIC < 2.5 μM), a pathogenic fungus of shrimp, but lower antimicrobial activity against Gram (−) bacteria, Vibrio sp. (40 μM < MIC < 80 μM). However, rLs-Stylicin1 is able to agglutinate Vibrio penaeicidae in vitro in agreement with its potent LPS-binding activity on immobilized LPS of V. penaeicidae (dissociation constant (Kd) of 9.6 × 10−8 M). This molecule with no evident homology to other hitherto described antimicrobial peptides but identified herein several species of penaeid shrimp is thought to be the first member of a shrimp antimicrobial peptide family, which we termed stylicins.