Prolines are not essential residues in the "barrel-stave" model for ion channels induced by alamethicin analogues.
In the "barrel-stave" model for voltage-gated alamethicin channels in planar lipid bilayers, proline residues, especially Pro14, are assumed to play a significant role. Taking advantage of a previous synthetic alamethicin analogue in which all eight alpha-aminoisobutyric acids were replaced by leucines, two new analogues were prepared in order to test the effects of Pro14 and Pro2 substitutions by alanines. The alpha-helical content of the three analogues in methanol solution remains predominant (between 63 and 80%). Macroscopic conductance experiments show that a high voltage dependence is conserved, although the apparent mean number of monomers forming the channels is significantly reduced when the substitution occurs at position 14. This is confirmed in single-channel experiments which further reveal faster fluctuations for the modified analogues. These results demonstrate that, although prolines, especially Pro14, are favorable residues for alamethicin-like events, they are not absolute prerequisites for the development of highly voltage-dependent multistate conductances.
Duclohier
H
H
URA 500 CNRS, Faculté des Sciences, Université de Rouen, Mont-Saint-Aignan, France.
Molle
G
G
Dugast
J Y
JY
Spach
G
G
D000408:Alamethicin / Q000031:analogs & derivatives* / Q000737:chemistry*; D000595:Amino Acid Sequence; D002942:Circular Dichroism; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials; D008954:Models, Biological; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D016339:Spectrometry, Mass, Fast Atom Bombardment
D007473:Ion Channels; D000408:Alamethicin