A novel antimicrobial function for a ribosomal peptide from rainbow trout skin.

An antimicrobial peptide was purified from skin secretions and epithelial cells of rainbow trout by cation exchange and reversed phase chromatography. Partial N-terminal amino acid sequence of the purified peptide revealed 100% identity with the first 11 residues of a 40S ribosomal peptide from medaka fish. Its molecular mass, determined by matrix-associated laser desorption/ionisation mass spectrometry, was found to be 6676.6Da. These results indicate that this antimicrobial peptide is likely to be the 40S ribosomal protein S30. It is active at submicromolar concentrations, with an effective 50% reduction concentration of 0.02-0.04 microM against Planococcus citreus. Thus, in addition to its conventional function in the cell as part of the small ribosomal subunit, this peptide may play a role in protection against intracellular or extracellular pathogens.