SYNTHESIS AND SOLUTION STRUCTURE OF THE ANTIMICROBIAL PEPTIDE PROTEGRIN-1

Protegrins are members of a family of five Cys-rich, cationic antimicr obial peptides recently isolated from porcine cells. We have synthesis ed an 18-amino-acid peptide that corresponds to protegrin-1. After Cys oxidation, the peptide has bactericidal activity against gram-positiv e and gram-negative bacteria, similar to that described for the natura l peptide. The solution structure of protegrin-1 was investigated by m eans of H-1-NMR spectroscopy in water and in (CD3)(2)SO, with distance -geometry and simulated-annealing calculations. The C6-C15 and C8-C13 disulfide pattern was determined on the basis of NMR-derived constrain ts. These two parallel disulfide bridges stabilised a beta-sheet struc ture which comprised two antiparallel strands (residues 5-9 and 12-16) linked by a distorted beta-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 str uctural feature shared with tachyplesin-1, a related peptide which dis plays cytolytic activity, and, to a lesser extent, with mammalian defe nsins. These findings led us to assume that the distribution pattern c ould be required for the cytolytic activity of these peptides.