Purification and primary structure of two isoforms of arenicin, a novel antimicrobial peptide from marine polychaeta Arenicola marina

Two novel 21-residue antimicrobial peptides, arenicin-1 and arenicin-2, exhibiting activity against Gram-positive and Gram-negative bacteria and fungi, were purified from coelomocytes of marine polychaeta Arenicola marina (lugworm) by preparative gel electrophoresis and RP-HPLC. Molecular masses (2758.3 and 2772.3 Da) and complete amino acid sequences (RWCVYAYVRVRGVLVRYRRCW and RWCVYAYVRIRGVLVRYRRCW) were determined for each isoform. Each arenicin has one disulfide bond (Cys3-Cys20). The total RNA was isolated from the lugworm coelomocytes, RT-PCR and cloning were performed, and cDNA was sequenced. A 202-residue preproarenicin contains a putative signal peptide (25 amino acids) and a long prodomain. Arenicins have no structure similarity to any previously identified antimicrobial peptides.