TRANSMEMBRANE CHANNEL ACTIVITY OF GRAMICIDIN-A ANALOGS - EFFECTS OF MODIFICATION AND DELETION OF THE AMINO-TERMINAL RESIDUE

The relationship between the nature of the side-chain at position 1 and the activity of the gramicidin A channel was investigated. The N-formyl group was removed, one round of an Edman degradation was carried out, and a new N-formyl residue was inserted in place of N-formyl-l-valine. The conductance properties of semisynthetic gramicidins containing N-formyl derivatives of d-valine, desvaline, glycine, cysteine, S-methyl-l-cysteine, S-carboxamidomethyl-l-cysteine, S-(spin-labeled)-l-cysteine, p-iodo-l-phenylalanine, and p-fluoro-l-phenylalanine were investigated. We found that the nature of the side-chain at position 1 markedly affects channel activity. A highly hydrophobic l-residue is required. © 1979.