Voltage activated ion channels formed by a synthetic α-helical peptide:- determination of channel stoichiometry and molecular modelling of peptide conformation
Mellor IR., Kerr ID., Sansom MSP., Sukumar M., Balaram P.
We designed and synthesized an 18 residue peptide (MS18) similar to the channel forming fungal antibiotic alamethicin. MS18 formed ion channels in lipid bilayers exhibiting a low discrete conductance level of 55 pS and brief openings to many other conductance levels. Channel formation was markedly dopondonl on transbilayer voltage with macroscopic conductance increasing exponentially beyond an activation voltage. The activation voltage was higher for lower concentrations of peptide. The relationship between conductance, voltage and peptide concentration was used to calculate the mean number of peptide monomers forming the MS18 channel. This gave an estimate of 4 MS18 monomers per channel. Molecular modeling of MS18 revealed a predominantly α-helical structure.