The NMR solution structure of the ion channel peptaibol chrysospermin C bound to dodecylphosphocholine micelles

Chrysospermin C is a 19-residue peptaibol capable of forming transmembrane ion channels in phospholipid bilayers. The conformation of chrysospermin C bound to dodecylphosphocholine micelles has been solved using heteronuclear NMR spectroscopy. Selective N-15-labeling and C-13-labeling of specific al pha-aminoisobutyric acid residues was used to obtain complete stereospecifi c assignments for all eight alpha-aminoisobutyric acid residues. Structures were calculated using 339 distance constraints and 40 angle constraints ob tained from NMR data. The NMR structures superimpose with mean global rmsd values to the mean structure of 0.27 Angstrom (backbone heavy atoms) and 0. 42 Angstrom (all heavy atoms). Chrysospermin C bound to decylphosphocholine micelles displays two well-defined helices at the N-terminus (residues Phe 1-Aib9) and C-terminus (Aib13-Trp-ol19). A slight bend preceding Pro14, i.e . encompassing residues 10-12, results in an angle of approximate to 38 deg rees between the mean axes of the two helical regions. The bend structure o bserved for chrysospermin C is compatible with the sequences of all 18 long peptaibols and may represent a common 'active' conformation. The structure of chrysospermin C shows clear hydrophobic and hydrophilic surfaces which would be appropriate for the formation of oligomeric ion channels.