The topologies of zervamicin II and alamethicin, labeled with (15)N uniformly, selectively, or specifically, have been investigated by oriented proton-decoupled (15)N solid-state NMR spectroscopy. Whereas at lipid-to-peptide (L/P) ratios of 50 (wt/wt) zervamicin II exhibits transmembrane alignments in 1,2-dicapryl (di-C10:0-PC) and 1,2-dilauroyl (di-C12:0-PC) phosphatidylcholine bilayers, it adopts orientations predominantly parallel to the membrane surface when the lengths of the fatty acyl chains are extended. The orientational order of zervamicin II increases with higher phospholipid concentrations, and considerable line narrowing is obtained in di-C10:0-PC/zervamicin II membranes at L/P ratios of 100 (wt/wt). In contrast to zervamicin, alamethicin is transmembrane throughout most, if not all, of its length when reconstituted into 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers. The (31)P solid-state NMR spectra of all phospholipid/peptaibol samples investigated show a high degree of headgroup order, indicating that the peptides do not distort the bilayer structure. The observed differences in peptide orientation between zervamicin and alamethicin are discussed with reference to differences in their lengths, helical conformations, distribution of (hydroxy)proline residues, and hydrophobic moments. Possible implications for peptaibol voltage-gating are also described.

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Spatial structure of the membrane channel-forming hexadecapeptide, zervamicin IIB, was studied by NMR spectroscopy in mixed solvents of different polarity ranging from CDCl 3 /CD 3 OH (9:1, v/v) to CD 3 OH/H 2 O (1:1, v/v). The results show that in all solvents used the peptide has a very similar structure that is a bent amphiphilic helix with a mean backbone root mean square deviation (rmsd) value of ca. 0.3 A î . Side chains of Trp 1 , Ile 2 , Gln 3 , Ile 5 and Thr 6 are mobile. The results are discussed in relation to the validity of the obtained structure to serve as a building block of zervamicin IIB ion channels.z 2000 Federation of European Biochemical Societies.