This is a family of antimicrobial peptides found in Stela clava (Sea squirt). Family members are alpha-helical phenylalanine-rich antimicrobial peptides effective against a panel of Gram-negative and Gram-positive bacteria. Styelin contains unusual amino acids such as dihydroxyarginine, dihydroxylysine, 6-bromotryptophan, and 3,4-dihydroxyphenylalanine which are important for the antimicrobial activity at high salt concentrations [1] [2].

1: Marine Antimicrobial Peptides: Nature Provides Templates for the Design of Novel Compounds against Pathogenic Bacteria. Falanga A, Lombardi L, Franci G, Vitiello M, Iovene MR, Morelli G, Galdiero M, Galdiero S; Int J Mol Sci. 2016; [Epub ahead of print] PMID:27213366

2: Styelin D, an extensively modified antimicrobial peptide from ascidian hemocytes. Taylor SW, Craig AG, Fischer WH, Park M, Lehrer RI; J Biol Chem. 2000;275:38417-38426. PMID:10978343