The significance of the gramicidin channel, its structural elements, and the importance of the peptide libration mechanism are reviewed. Elemental ionic processes of the single-channel currents are considered, which indicate the possibility of two-and three-site models. Data are presented which demonstrate the absence of interactions required for the three-site model, and the resulting freeenergy profile for the two-site model is given for the most probable conducting state. The need to extend analyses to include an understanding of multiple conformational states is outlined, and results from approximate conformational energy calculations are presented showing that there are numerous low-energy conformations for the side chains of gramicidin. Specifically the interactions between L.Trp9 and L.Trpl=, side chains and between D-Leud. . .D-LeUjo are analyzed to show the existence of several energy minima separated by appreciable barriers. These findings provide the basis for understanding facilitated entry of the second ion into the channel and the occurrence of lipid-dependent dispersion of conductance states. Finally perspectives of the molecular mechanism of anesthetics are discussed relevant to the gramicidin channel mean lifetime and single-channel currents.

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