Characterization of a type of β-bend ribbon spiral generated by the repeating (Xaa-Yaa-Aib-Pro) motif: The solution structure of harzianin HC IX, a 14-residue peptaibol forming voltage-dependent ion channels

摘要

The three-dimensional structure of harzianin HC IX in methanol solution was determined using nuclear magnetic resonance spectroscopy. The peptide backbone of harzianin HC IX consisted of a ribbon of overlapping β-turns twisted into a continuous spiral from Asn~2 to Leuo~l2 and forming a 26 angstroms long helix-like structure. This structure was slightly amphipathic, with the three Aib-Pro motifs aligned on the less hydrophobic face of the spiral where the side chain was present, while the more hydrophobic bulk side chains of leucines, isoleucine, isovaline, and leucinol were located on the concave side. The repetitive (Xaa-Yaa-Aib-Pro) tetrapeptide subunit, making up the peptide sequence was characterized by four sets of torsional angles.