title: Stereospecificity of aminoglycoside-ribosomal interactions.
abstract: Aminoglycoside antibiotics bind to the A-site decoding region of bacterial rRNA causing mistranslation and/or premature message termination. Aminoglycoside binding to A-site RNA decoding region constructs is established here to be only weakly stereospecific. Mirror-image prokaryotic A-site decoding region constructs were prepared in the natural D-series and the enantiomeric L-series and tested for binding to a series of aminoglycosides. In general, aminoglycosides bind to the D-series decoding region constructs with 2-3-fold higher affinities than they bind to the enantiomeric L-series. Moreover, L-neamine, the enantiomer of naturally occurring D-neamine, was prepared and shown to bind approximately 2-fold more weakly than D-neamine to the natural series decoding region construct, a result consistent with weakly stereospecific binding. The binding of naturally occurring D-neamine and its synthetic L-enantiomer was further evaluated with respect to binding to prokaryotic and eukaryotic ribosomes. Here, weak stereospecifcity was again observed with L-neamine being the more potent binder by a factor of approximately 2. However, on a functional level, unnatural L-neamine proved to inhibit in vitro translation with significantly lower potency (approximately 5-fold) than D-neamine. In addition, both L- and D-neamine are bacteriocidal toward Gram-(-) bacteria. L-Neamine inhibits the growth of E. coli and P. aeruginosa with 8- and 3-fold higher MIC than D-neamine. Interestingly, L-neamine also inhibits the growth of aminoglycoside-resistant E. coli, which expresses a kinase able to phosphorylate and detoxify aminoglycosides of the D-series. These observations suggest that mirror-image aminoglycosides may avoid certain forms of enzyme-mediated resistance.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 45 Shattuck Street, Boston, Massachusetts 02115, USA.
authors.forename: Do Hyun
authors.initials: DH
authors.lastname: Ryu
authors.forename: Alexander
authors.initials: A
authors.lastname: Litovchick
authors.forename: Robert R
authors.initials: RR
authors.lastname: Rando
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D001667:Binding, Competitive; D005454:Fluorescence Polarization / Q000379:methods; D005601:Framycetin / Q000737:chemistry / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D009843:Oligoribonucleotides / Q000138:chemical synthesis; D010303:Paromomycin / Q000737:chemistry; D014176:Protein Biosynthesis / Q000187:drug effects; D012329:RNA, Bacterial / Q000037:antagonists & inhibitors / Q000138:chemical synthesis / Q000737:chemistry; D012331:RNA, Fungal / Q000037:antagonists & inhibitors / Q000138:chemical synthesis / Q000737:chemistry; D012335:RNA, Ribosomal / Q000037:antagonists & inhibitors / Q000138:chemical synthesis / Q000737:chemistry*; D012235:Rhodamines / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D014031:Tobramycin / Q000737:chemistry
chemical_list: C437523:5-carboxytetramethylrhodamine; D000900:Anti-Bacterial Agents; D009843:Oligoribonucleotides; D012329:RNA, Bacterial; D012331:RNA, Fungal; D012335:RNA, Ribosomal; D012235:Rhodamines; D005601:Framycetin; D010303:Paromomycin; D014031:Tobramycin