title: What determines the activity of antimicrobial and cytolytic peptides in model membranes.
abstract: We previously proposed three hypotheses relating the mechanism of antimicrobial and cytolytic peptides in model membranes to the Gibbs free energies of binding and insertion into the membrane [Almeida, P. F., and Pokorny, A. (2009) Biochemistry 48, 8083-8093]. Two sets of peptides were designed to test those hypotheses, by mutating of the sequences of δ-lysin, cecropin A, and magainin 2. Peptide binding and activity were measured on phosphatidylcholine membranes. In the first set, the peptide charge was changed by mutating basic to acidic residues or vice versa, but the amino acid sequence was not altered much otherwise. The type of dye release changed from graded to all-or-none according to prediction. However, location of charged residues in the sequence with the correct spacing to form salt bridges failed to improve binding. In the second set, the charged and other key residues were kept in the same positions, whereas most of the sequence was significantly but conservatively simplified, maintaining the same hydrophobicity and amphipathicity. This set behaved completely different from predicted. The type of release, which was expected to be maintained, changed dramatically from all-or-none to graded in the mutants of cecropin and magainin. Finally, contrary to the hypotheses, the results indicate that the Gibbs energy of binding to the membrane, not the Gibbs energy of insertion, is the primary determinant of peptide activity.
authors.affiliation: Department of Chemistry and Biochemistry, University of North Carolina, Wilmington, North Carolina 28403, USA.
authors.forename: Kim S
authors.initials: KS
authors.lastname: Clark
authors.forename: James
authors.initials: J
authors.lastname: Svetlovics
authors.forename: Alesia N
authors.initials: AN
authors.lastname: McKeown
authors.forename: Laura
authors.initials: L
authors.lastname: Huskins
authors.forename: Paulo F
authors.initials: PF
authors.lastname: Almeida
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D019004:Galanin / Q000737:chemistry / Q000378:metabolism; D006460:Hemolysin Proteins / Q000737:chemistry / Q000378:metabolism; D054806:Magainins / Q000737:chemistry / Q000378:metabolism; D008567:Membranes, Artificial; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D055672:Static Electricity; D013816:Thermodynamics; D014862:Wasp Venoms / Q000737:chemistry / Q000378:metabolism; D029867:Xenopus Proteins / Q000737:chemistry / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D006460:Hemolysin Proteins; D054806:Magainins; D008567:Membranes, Artificial; D010455:Peptides; D010713:Phosphatidylcholines; D011993:Recombinant Fusion Proteins; D014862:Wasp Venoms; D029867:Xenopus Proteins; C110068:transportan; C053301:magainin 2 peptide, Xenopus; C025994:delta hemolysin protein, Staphylococcus aureus; D019004:Galanin