Structure–function relationships of temporins, small antimicrobialpeptides from amphibian skin

Abstract

Temporins, antimicrobial peptides of 10±13 residues, were isolated from secretions 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 secrete on its skin other antimicrobial peptides similar to those found in different 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 of large-size molecules from the bacterial cells; temporin H renders both the outer and inner membrane of bacteria permeable to hydrophobic substances of low molecular mass; and temporin D, although devoid of antibacterial activity, 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.

A Synergism between Temporins toward Gram-negative Bacteria Overcomes Resistance Imposed by the Lipopolysaccharide Protective Layer

“…Among these bacteria is Aeromonas hydrophila, which is associated with the global decline of amphibians (44,45), and which is resistant to the majority of natural AMPs (36,45). Our data suggest that temporin L prevents the aggregation of temporins A and B within LPS, thus allowing their translocation across the outer membrane into the cytoplasmic membrane.…”

Interaction of Antimicrobial Peptide Temporin L with Lipopolysaccharide In Vitro and in Experimental Rat Models of Septic Shock Caused by Gram-Negative Bacteria

“…Synthetic temporin L was purchased from SynPep Corporation (Dublin, Calif.). The purity of the peptide and its sequence and concentration were determined as previously described (33). It was either dissolved in distilled H 2 O at 20 times the required maximal concentration or dissolved in 20% ethanol.…”

“…The spectrum of antimicrobial activity displayed by temporins is interestingly vast and diverse. They are generally most active against gram-positive bacteria, but some show considerable activity also against gram-negative bacteria and fungal pathogens, including Candida albicans and Batrachochytrium dendrobatidis, a pathogen associated with global amphibian declines (33,44,45,49). Furthermore, selected temporins have been recently shown to exert a potent killing activity against the human parasitic protozoan Leishmania (34).…”

“…Studies aimed at understanding the killing mechanism of temporins have ascertained that these peptides alter the permeability of bacterial cell membrane in a dose-dependent manner without destroying cell integrity, leading to leakage of cytosolic content and cell death (32). Biophysical investigations have been performed using membrane model systems confirming that temporins bind and permeate membranes with different lipid compositions (33,44,58,59). However, the possibility that temporins might act in vivo by translocating through the bacterial cell membrane and interacting with an intracellular target cannot be excluded at present.…”

Antimicrobial peptides

“…Many peptides of this group have been classified as "pore-forming" such as alamethicin, cecropin, PGLa, magainin, melittin and mastoparan. [21][22][23] (2) cyclic peptides with b-sheet structure that form predominantly b-sheets including coupled b-strands due to the presence of two or more disulfide bonds. Although being antifungal in some cases, 11,24 they are often characterized as antibacterial peptides.…”