Biophysical study of the structure and dynamics of the antimicrobial peptide maximin 1.

Maximin 1 is a cationic, amphipathic antimicrobial peptide found in the skin secretions and brains of the Chinese red belly toad Bombina maxima. The 27 amino acid residue-long peptide is biologically interesting as it possesses a variety of biological activities, including antibacterial, antifungal, antiviral, antitumour and spermicidal activities. Its three-dimensional structural model was obtained in a 50/50% water/2,2,2-trifluoroethanol-d3 mixture using two-dimensional NMR spectroscopy. Maximin 1 was found to adopt an α-helical structure from residue Ile2 to Ala26 . The peptide is amphipathic, showing a clear separation between polar and non-polar residues. The interactions with sodium dodecyl sulfate micelles, a widely-used bacterial membrane-mimicking environment, were modelled using molecular dynamics simulations. The peptide maintains an α-helical conformation, occasionally displaying a flexibility around the Gly9 and Gly16 residues, which is likely responsible for the peptide's low haemolytic activity. It is found to preferentially adopt a position parallel to the micellar surface, establishing a number of hydrophobic and electrostatic interactions with the micelle.

Conformation and membrane interaction studies of the potent antimicrobial and anticancer peptide palustrin-Ca.

Palustrin-Ca (GFLDIIKDTGKEFAVKILNNLKCKLAGGCPP) is a host defence peptide with potent antimicrobial and anticancer activities, first isolated from the skin of the American bullfrog Lithobates catesbeianus. The peptide is 31 amino acid residues long, cationic and amphipathic. Two-dimensional NMR spectroscopy was employed to characterise its three-dimensional structure in a 50/50% water/2,2,2-trifluoroethanol-[Formula: see text] mixture. The structure is defined by an [Formula: see text]-helix that spans between Ile[Formula: see text]-Ala[Formula: see text], and a cyclic disulfide-bridged domain at the C-terminal end of the peptide sequence, between residues 23 and 29. A molecular dynamics simulation was employed to model the peptide's interactions with sodium dodecyl sulfate micelles, a widely used bacterial membrane-mimicking environment. Throughout the simulation, the peptide was found to maintain its [Formula: see text]-helical conformation between residues Ile[Formula: see text]-Ala[Formula: see text], while adopting a position parallel to the surface to micelle, which is energetically-favourable due to many hydrophobic and electrostatic contacts with the micelle.