Solvent-induced α- to 3(10)-helix transition of an amphiphilic peptide.

The amphiphilic peptide of the triacylglycerol lipase derived from Pseudomonas aeruginosa plays a critical role in guarding the gate for ligand access. Conformations of this peptide at several water-oil interfaces and in protein environments were compared using atomistic simulations with explicit solvents. In oil-containing solvents, this peptide is able to retain a folded structure. Interestingly, when the peptide is immersed in a low-polarity solvent environment, it exhibits a "coalesced" helix structure, which has both α- and 3(10)-helix components. The observation that the 3(10)-helical conformation is populated in a highly nonpolar environment is consistent with a previous report on polymethylalanine. Frequent interconversions of the secondary structure (between α-helix and 3(10)-helix) of the peptide are also observed. We further studied how this solvent-induced structural transition may be connected to the trigger mechanism of lipase gating and how the lipase senses the hydrophobic-hydrophilic interface.