title: Cis-acting resistance peptides reveal dual ribosome inhibitory action of the macrolide josamycin.
abstract: Macrolide antibiotics block the entrance of nascent peptides to the peptide exit tunnel of the large ribosomal subunit. Expression of specific cis-acting peptides confers low-level macrolide-resistance. We show that, in the case of josamycin, peptide expression does not eject josamycin from the ribosome, implying a peptide resistance mechanism different from that previously suggested for erythromycin. We find dipeptide formation and dipeptidyl-tRNA drop-off in the presence of josamycin to be much slower during translation of resistance than of control mRNAs. We demonstrate low-level josamycin resistance by over-expression of peptidyl-tRNA hydrolase. These findings suggest dual growth-inhibitory action of josamycin by (i) direct inhibition of peptide-elongation and (ii) indirect inhibition of peptide-elongation through rapid peptidyl-tRNA drop-off, leading to depletion of tRNA isoacceptors available for protein synthesis. We propose that josamycin resistance peptide expression brings ribosomes into a "quarantine" state with small drop-off rate, thereby eliminating the josamycin dependent depletion of tRNA isoacceptors in the protein-synthesis-active state.
authors.affiliation: Department of Cell and Molecular Biology, Uppsala University, BMC, Sweden. martin.lovmar@astratech.com
authors.forename: Martin
authors.initials: M
authors.lastname: Lovmar
authors.forename: Vladimir
authors.initials: V
authors.lastname: Vimberg
authors.forename: Eliisa
authors.initials: E
authors.lastname: Lukk
authors.forename: Karin
authors.initials: K
authors.lastname: Nilsson
authors.forename: Tanel
authors.initials: T
authors.lastname: Tenson
authors.forename: Måns
authors.initials: M
authors.lastname: Ehrenberg
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D049109:Cell Proliferation / Q000187:drug effects; D004151:Dipeptides / Q000096:biosynthesis; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D015570:Josamycin / Q000494:pharmacology*; D016366:Open Reading Frames / Q000235:genetics; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D010458:Peptidyl Transferases / Q000037:antagonists & inhibitors; D014176:Protein Biosynthesis / Q000187:drug effects; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D004151:Dipeptides; D010455:Peptides; D012343:RNA, Transfer; D010458:Peptidyl Transferases; D015570:Josamycin