Solvent-Induced α- to 3₁₀-Helix Transition of an Amphiphilic Peptide

The amphiphilic peptide of the triacylglycerol lipase derived from <i>Pseudomonas aeruginosa</i> 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 3₁₀-helix components. The observation that the 3₁₀-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 3₁₀-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

Effects of Branched O‑Glycosylation on a Semiflexible Peptide Linker

Glycosylation is an essential modification of proteins and lipids by the addition of carbohydrate residues. These attached carbohydrates range from single monomers to elaborate branched glycans. Here, we examine how the level of glycosylation affects the conformation of a semiflexible peptide linker using the example of the hinge peptide from immunoglobulin A. Three sets of atomistic models of this hinge peptide with varying degrees of glycosylation are constructed to probe how glycosylation affects the physical properties of the linker. We found that glycosylation greatly altered the predominant conformations of the peptide, causing it to become elongated in reference to the unglycosylated form. Furthermore, glycosylation restricts the conformational exploration of the peptide. At the residue level, glycans are found to introduce a bias for the formation of more extended secondary structural elements for glycosylated serines. Additionally, the flexibility of this semiflexible proline-rich peptide is significantly reduced by glycosylation