CONTRIBUTION OF PROLINE-14 TO THE STRUCTURE AND ACTIONS OF MELITTIN

The structure and dynamic properties of bee venom melittin and a synthetic analogue, [Ala14]-melittin (melittin P14A), are compared, using high resolution H-1 nuclear magnetic resonance (NMR) spectroscopy and amide exchange measurements in methanol. P14A is shown to adopt a regular, stable alpha-helical conformation in solution without the flexibility around the Pro-14 residue found in melittin. P14A has twice the hemolytic activity of melittin but is less able to induce voltage-dependent ion conductance in planar bilayers. The results indicate that helix flexibility afforded by the Pro-14 residue promotes the ability of melittin to adopt the transbilayer associates thought to underlie ion translocation.