Interaction of ladder-shaped polyethers with transmembrane α-helix of glycophorin A as evidenced by saturation transfer difference NMR and surface plasmon resonance

Ladder-shaped polyether (LSP) compounds are thought to interact with transmembrane α-helices, but direct evidence has scarcely obtained for these interactions. We adopted a transmembrane α-helix of glycophorin A, and quantitatively evaluated its interaction with LSPs such as yessotoxin (YTX), desulfated YTX and artificial LSPs, using surface plasmon resonance and saturation transfer difference NMR. As a result, dissociation constants (K_D) of YTX and desulfated YTX to a transmembrane domain peptide of glycophorin A were determined to be in the submillimolar range. Furthermore, in saturation transfer difference NMR, the signals at the polyene side chain and the angular methyl groups of YTX were significantly attenuated, which probably comprised an interacting interface of LSPs with a transmembrane α-helix. These results suggest that hydrophobic interaction plays an important role in molecular recognition of the α-helix peptide by LSPs.