title: Design, synthesis, and characterization of a cationic peptide that binds to nucleic acids and permeabilizes bilayers.
abstract: We have designed a cationic amphipathic peptide, KALA (WEAKLAKALAKALAKHLAKALAKALKACEA), that binds to DNA, destabilizes membranes, and mediates DNA transfection. KALA undergoes a pH-dependent random coil to amphipathic alpha-helical conformational change as the pH is increased from 5.0 to 7.5. One face displays hydrophobic leucine residues, and the opposite face displays hydrophilic lysine residues. KALA-mediated release of entrapped aqueous contents from neutral and negatively charged liposomes increases with increasing helical content. KALA binds to oligonucleotides or plasmid DNA and retards their migration in gel electrophoresis. It displaces 50% of ethidium bromide from DNA at a charge ratio (+/-) of 0.9/1. In cultured cells, KALA assists oligonucleotide nuclear delivery when complexes are prepared at a 10/1 (+/-) charge ratio. KALA/DNA (10/1)(+/-) complexes mediate transfection of a variety of cell lines. The KALA sequence provides a starting point for a family of peptides that incorporate other functions to improve DNA delivery systems.
authors.affiliation: Department of Biopharmaceutical Sciences and Pharmaceutical Chemistry, University of California, San Francisco 94143-0446, USA.
authors.forename: T B
authors.initials: TB
authors.lastname: Wyman
authors.forename: F
authors.initials: F
authors.lastname: Nicol
authors.forename: O
authors.initials: O
authors.lastname: Zelphati
authors.forename: P V
authors.initials: PV
authors.lastname: Scaria
authors.forename: C
authors.initials: C
authors.lastname: Plank
authors.forename: F C
authors.initials: FC
authors.lastname: Szoka
mesh_terms: D000595:Amino Acid Sequence; D002412:Cations / Q000378:metabolism; D002478:Cells, Cultured; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism*; D015195:Drug Design; D004587:Electrophoresis, Agar Gel; D004996:Ethidium / Q000378:metabolism; D005453:Fluorescence; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism*; D010539:Permeability; D017433:Protein Structure, Secondary; D014162:Transfection / Q000235:genetics; D014364:Tryptophan / Q000378:metabolism
chemical_list: D002412:Cations; D004268:DNA-Binding Proteins; D005456:Fluorescent Dyes; C105114:KALA amphipathic peptide; D008051:Lipid Bilayers; D008081:Liposomes; D010455:Peptides; D014364:Tryptophan; D004247:DNA; D008156:Luciferases; D004996:Ethidium