title: Engineered salt-insensitive alpha-defensins with end-to-end circularized structures.
abstract: We designed a retro-isomer and seven circularized "beta-tile" peptide analogs of a typical rabbit alpha-defensin, NP-1. The analogs retained defensin-like architecture after the characteristic end-to-end, Cys(3,31) (C I:C VI), alpha-defensin disulfide bond was replaced by a backbone peptide bond. The retro-isomer of NP-1 was as active as the parent compound, suggesting that overall topology and amphipathicity governed its antimicrobial activity. A beta-tile design with or without a single cross-bracing disulfide bond sufficed for antimicrobial activity, and some of the analogs retained activity against Escherichia coli and Salmonella typhimurium in NaCl concentrations that rendered NP-1 inactive. The new molecules had clustered positive charges resembling those in protegrins and tachyplesins, but were less cytotoxic. Such simplified alpha-defensin analogs minimize problems encountered during the oxidative folding of three-disulfide defensins. In addition, they are readily accessible to a novel thia zip cyclization procedure applicable to large unprotected peptide precursors of 31 amino acids in aqueous solutions. Collectively, these findings provide new and improved methodology to create salt-insensitive defensin-like peptides for application against bacterial diseases.
authors.affiliation: Department of Microbiology and Immunology, Vanderbilt University, Nashville, Tennessee 37232-2363, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Yu
authors.forename: R I
authors.initials: RI
authors.lastname: Lehrer
authors.forename: J P
authors.initials: JP
authors.lastname: Tam
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis* / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides; D023082:Defensins; D004220:Disulfides / Q000737:chemistry; D004926:Escherichia coli / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000138:chemical synthesis*; D015202:Protein Engineering; D011506:Proteins / Q000138:chemical synthesis* / Q000737:chemistry; D011817:Rabbits; D012486:Salmonella typhimurium / Q000187:drug effects; D012492:Salts / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D023084:alpha-Defensins
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D023082:Defensins; D004220:Disulfides; D010456:Peptides, Cyclic; D011506:Proteins; D012492:Salts; D023084:alpha-Defensins; C406564:defensin NP-1