Structure-function relationships of temporins, small antimicrobialpeptidesfrom amphibian skin

Temporins, antimicrobial peptides of 10-13 residues, were isolated from sec retions of Rana temporaria [Simmaco, M., Mignogna, G., Canofeni, S., Miele, R., Mangoni, M.L. & Barra, D. (1996) Eur. J. Biochem. 242, 788-792]. These molecules are specific to this amphibian species, which is also able to se crete on its skin other antimicrobial peptides similar to those found in di fferent Rana species. The effect of temporins A, B and D (13 residues, net charge +2), and H (10 residues, net charge +1 and +2, respectively) against both artificial membranes of differing lipid composition and bacteria has been investigated in order to gain insight into their mechanisms of action. The results indicate that: the lytic activity of temporins is not greatly affected by the membrane composition; temporins A and B allow the leakage o f large-size molecules from the bacterial cells; temporin H renders both th e outer and inner membrane of bacteria permeable to hydrophobic substances of low molecular mass; and temporin D, although devoid of antibacterial act ivity, has a cytotoxic effect on erythrocytes. The results allow important conclusions to be drawn about the minimal structural requirements for lytic efficiency and specificity of temporins.