title: Conformational Fine-Tuning of Pore-Forming Peptide Potency and Selectivity.
abstract: To better understand the sequence-structure-function relationships that control the activity and selectivity of membrane-permeabilizing peptides, we screened a peptide library, based on the archetypal pore-former melittin, for loss-of-function variants. This was accomplished by assaying library members for failure to cause leakage of entrapped contents from synthetic lipid vesicles at a peptide-to-lipid ratio of 1:20, 10-fold higher than the concentration at which melittin efficiently permeabilizes the same vesicles. Surprisingly, about one-third of the library members are inactive under these conditions. In the negative peptides, two changes of hydrophobic residues to glycine were especially abundant. We show that loss-of-function activity can be completely recapitulated by a single-residue change of the leucine at position 16 to glycine. Unlike the potently cytolytic melittin, the loss-of-function peptides, including the single-site variant, are essentially inactive against phosphatidylcholine vesicles and multiple types of eukaryotic cells. Loss of function is shown to result from a shift in the binding-folding equilibrium away from the active, bound, α-helical state toward the inactive, unbound, random-coil state. Accordingly, the addition of anionic lipids to synthetic lipid vesicles restored binding, α-helical secondary structure, and potent activity of the "negative" peptides. While nontoxic to mammalian cells, the single-site variant has potent bactericidal activity, consistent with the anionic nature of bacterial membranes. The results show that conformational fine-tuning of helical pore-forming peptides is a powerful way to modulate their activity and selectivity.
authors.affiliation: Department of Biochemistry and Molecular Biology, Tulane University School of Medicine , New Orleans, Louisiana 70112, United States.
authors.forename: Aram J
authors.initials: AJ
authors.lastname: Krauson
authors.affiliation: Department of Biochemistry and Molecular Biology, Tulane University School of Medicine , New Orleans, Louisiana 70112, United States.
authors.forename: O Morgan
authors.initials: OM
authors.lastname: Hall
authors.affiliation: Department of Biochemistry and Molecular Biology, Tulane University School of Medicine , New Orleans, Louisiana 70112, United States.
authors.forename: Taylor
authors.initials: T
authors.lastname: Fuselier
authors.affiliation: Department of Biochemistry and Molecular Biology, Tulane University School of Medicine , New Orleans, Louisiana 70112, United States.
authors.forename: Charles G
authors.initials: CG
authors.lastname: Starr
authors.affiliation: Department of Biochemistry and Molecular Biology, Tulane University School of Medicine , New Orleans, Louisiana 70112, United States.
authors.forename: W Berkeley
authors.initials: WB
authors.lastname: Kauffman
authors.affiliation: Department of Biochemistry and Molecular Biology, Tulane University School of Medicine , New Orleans, Louisiana 70112, United States.
authors.forename: William C
authors.initials: WC
authors.lastname: Wimley
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D004912:Erythrocytes / Q000187:drug effects; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology; D011487:Protein Conformation
chemical_list: D000900:Anti-Bacterial Agents; D010455:Peptides