UNUSUALLY STABLE HELICAL KINK IN THE ANTIMICROBIAL PEPTIDE - A DERIVATIVE OF GAEGURIN

The structure of an active analog of the antibacterial peptide gaeguri n was investigated by CD and NMR spectroscopy. The NOE connectivities showed that 21 out of 24 residues formed an alpha-helix despite the pr esence of a central proline. CD and NMR analysis indicates that the he lix is in fast equilibrium with random coil, From chemical shift analy sis of the amide protons, the distances of hydrogen bonding in the hel ix were calculated, and manifested obvious periodicity which implied a kink in the middle of the helix. 1D amide proton exchange experiments provided further evidence of an exceptionally stable kink. It is infe rred that this kink is important not only to the function of the pepti de but also to the early stage of the folding as a nucleation site.