THE PORE DIMENSIONS OF GRAMICIDIN-A

The ion channel forming peptide gramicidin A adopts a number of distin ct conformations in different environments. We have developed a new me thod to analyze and display the pore dimensions of ion channels. The p rocedure is applied to two x-ray crystal structures of gramicidin that adopt distinct antiparallel double helical dimer conformations and a nuclear magnetic resonance (NMR) structure for the beta6.3 NH2-termina l to NH2-terminal dimer. The results are discussed with reference to i on conductance properties and dependence of pore dimensions on the env ironment.