Résumé
Protegrins are members of a family of five Cys‐rich, cationic antimicrobial peptides recently isolated from porcine cells. We have synthesised an 18‐amino‐acid peptide that corresponds to protegrin‐1. After Cys oxidation, the peptide has bactericidal activity against gram‐positive and gram‐negative bacteria, similar to that described for the natural peptide. The solution structure of protegrin‐1 was investigated by means of 1H‐NMR spectroscopy in water and in (CD3)2SO, with distance‐geometry and simulated‐annealing calculations. The C6‐C15 and C8‐C13 disulfide pattern was determined on the basis of NMR‐derived constraints. These two parallel disulfide bridges stabilised a β‐sheet structure which comprised two anti‐parallel strands (residues 5–9 and 12–16) linked by a distorted β‐turn (residues 9–12). The N‐terminus and C‐terminus were essentially disordered. The distribution of hydrophobic and hydrophilic residues at the peptide surface was found to be a structural feature shared with tachyplesin‐1, a related peptide which displays cytolytic activity, and, to a lesser extent, with mammalian defensins. These findings led us to assume that the distribution pattern could be required for the cytolytic activity of these peptides.