title: Ribosomal binding and antibacterial activity of ethylene glycol-bridged apidaecin Api137 and oncocin Onc112 conjugates.
abstract: Recent surveillance data on antimicrobial resistance predict the beginning of the post-antibiotic era with pan-resistant bacteria even overcoming polymyxin as the last available treatment option. Thus, new substances using novel modes of antimicrobial action are urgently needed to reduce this health threat. Antimicrobial peptides are part of the innate immune system of most vertebrates and invertebrates and accepted as valid substances for antibiotic drug development efforts. Especially, short proline-rich antimicrobial peptides (PrAMP) of insect origin have been optimized for activity against Gram-negative strains. They inhibit protein expression in bacteria by blocking the 70S ribosome exit tunnel (oncocin-type) or the assembly of the 50S subunit (apidaecin-type binding). Thus, apidaecin analog Api137 and oncocin analog Onc112 supposedly bind to different nearby or possibly partially overlapping binding sites. Here, we synthesized Api137/Onc112-conjugates bridged by ethylene glycol spacers of different length to probe synergistic activities and binding modes. Indeed, the antimicrobial activities against Escherichia coli and Pseudomonas aeruginosa improved for some constructs, although the conjugates did not bind better to the 70S ribosome of E. coli than Api137 and Onc112 using 5(6)-carboxyfluorescein-labelled Api137 and Onc112 in a competitive fluorescence polarization assay. In conclusion, Api137/Onc112-conjugates showed increased antimicrobial activities against P. aeruginosa and PrAMP-susceptible and -resistant E. coli most likely because of improved membrane interactions, whereas the interaction to the 70S ribosome was most likely not improved relying still on the independent apidaecin- and oncocin-type binding modes. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.
authors.affiliation: Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, Universität Leipzig, Deutscher Platz 5, 04103, Leipzig, Germany.|Center for Biotechnology and Biomedicine, Universität Leipzig, Deutscher Platz 5, 04103, Leipzig, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Goldbach
authors.affiliation: Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, Universität Leipzig, Deutscher Platz 5, 04103, Leipzig, Germany.|Center for Biotechnology and Biomedicine, Universität Leipzig, Deutscher Platz 5, 04103, Leipzig, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Knappe
authors.affiliation: Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, Universität Leipzig, Deutscher Platz 5, 04103, Leipzig, Germany.|Center for Biotechnology and Biomedicine, Universität Leipzig, Deutscher Platz 5, 04103, Leipzig, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Reinsdorf
authors.affiliation: Institute of Organic Chemistry, Faculty of Chemistry and Mineralogy, Universität Leipzig, Johannisallee 29, 04103, Leipzig, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Berg
authors.affiliation: Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, Universität Leipzig, Deutscher Platz 5, 04103, Leipzig, Germany.|Center for Biotechnology and Biomedicine, Universität Leipzig, Deutscher Platz 5, 04103, Leipzig, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Hoffmann
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D019855:Ethylene Glycol / Q000737:chemistry*; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D054681:Ribosome Subunits, Large, Bacterial / Q000187:drug effects / Q000378:metabolism*; D054680:Ribosome Subunits, Small, Bacterial / Q000187:drug effects / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D005452:Fluoresceins; D005456:Fluorescent Dyes; C551620:oncocin; C061361:apidaecin; C024098:6-carboxyfluorescein; D019855:Ethylene Glycol
keywords: 70S ribosome; Gram-negative bacteria; fluorescence polarization; proline-rich antimicrobial peptides