pH dependent conformation of physalaemin

The undecapeptide physalaemin was investigated by n.m.r. spectroscopy in DMSO solution under acidic and neutral conditions. Large changes of the NH chemical shifts and the temperature gradients of the NH protons occurred on going from pH 3.5 to pH 7.0 for residues around the charged amino acids Asp and Lys. At pH 3.5 the data are in accord with a flexible conformation of the peptide. The results at neutral pH are interpreted in terms of a folded structure having two interresidue and one intraresidue hydrogen bond. They include a beta turn with proline in position i + 1 and asparagine in position i + 2.