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 microM<MIC<2.5 microM), a pathogenic fungus of shrimp, but lower antimicrobial activity against Gram (-) bacteria, Vibrio sp. (40 microM<MIC<80 microM). 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 (K(d)) of 9.6x10(-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.