Toxicity of aminoglycoside antibiotics may be due to alternate binding of the human mitochondrial ribosomal RNA

Aminoglycoside antibiotics are a well-known antibiotic family used to treat various bacterial infections in humans and animals, but unfortunately have significant toxicity. These aminoglycoside antibiotics primarily bind to helix 44 of the bacterial small ribosomal subunit RNA at the tRNA receptor aminoacyl site and, thus inhibit protein synthesis by causing misreading or obstructing the translocation process (1). However, recent findings demonstrate that aminoglycosides bind helix 69 of the large subunit RNA as well. Little is known about the interaction of aminoglycosides with the homologous H69 rRNA hairpin of the human host and which may play a role inaminoglycoside toxicity. To gain insight, we compared aminoglycoside binding to the terminal hairpin ofhuman cytoplasmic, human mitochondrial, and Escherichia coli H69, and human mitochondrial and E. coli H44 using UV-monitored thermal stability analysis, circular dichroism (CD), and NMR structural studies. The UV thermal analysis shows that the overallbinding affinities of gentamicin and kanamycin A to the human cytoplasmic, human mitochondrial, and E. coli H69 were similar. CD and 1H 1D and 2D NMR results indicated that aminoglycoside binding enhances the conformational stability by increasing base stacking on human mitochondrial H69. The greater binding induced stability on human mitochondrial H69 and similar binding affinity to that of E. coli suggest that human mitochondrial H69 may be important to understanding the mechanism of aminoglycoside toxicity.