Effect of Mutations on the Binding of Kanamycin-B to RNA Hairpins Derived from the Mycobacterium tuberculosis Ribosomal A-Site

Biochemistry. 2015 Dec 29;54(51):7425-37. doi: 10.1021/acs.biochem.5b00710. Epub 2015 Dec 17.

Abstract

Kanamycin is an aminoglycoside antibiotic used in the treatment of drug-resistant tuberculosis. Mutations at the rRNA A-site have been associated with kanamycin resistance in Mycobacterium tuberculosis clinical isolates. Understanding the effect of these mutations on the conformation of the M. tuberculosis A-site is critical for understanding the mechanisms of antibiotic resistance in M. tuberculosis. In this work, we have studied RNA hairpins derived from the M. tuberculosis A-site, the wild type and three mutants at the following positions (M. tuberculosis/Escherichia coli numbering): A1400/1408 → G, C1401/1409 → U, and the double mutant G1483/1491 C1401/1409 → UA. Specifically, we used circular dichroism, ultraviolet spectroscopy, and fluorescence spectroscopy to characterize the conformation, stability, and binding affinity of kanamycin-B and other aminoglycoside antibiotics for these RNA hairpins. Our results show that the mutations affect the conformation of the decoding site, with the mutations at position 1401/1409 resulting in significant destabilizations. Interestingly, the mutants bind paromomycin with weaker affinity than the wild type, but they bind kanamycin-B with similar affinity than the wild type. The results suggest that the presence of mutations does not prevent kanamycin-B from binding. Instead, kanamycin may promote different interactions with a third partner in the mutants compared to the wild type. Furthermore, our results with longer and shorter hairpins suggest that the region of the A-site that varies among organisms may have modulating effects on the binding and interactions of the A-site.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / chemistry*
  • Circular Dichroism
  • Kanamycin / analogs & derivatives*
  • Kanamycin / chemistry
  • Molecular Structure
  • Mutation*
  • Mycobacterium tuberculosis / chemistry*
  • Mycobacterium tuberculosis / genetics
  • Nucleic Acid Conformation
  • RNA, Bacterial / chemistry*
  • RNA, Bacterial / genetics
  • Ribosomes / chemistry*
  • Spectrometry, Fluorescence
  • Spectrophotometry, Ultraviolet

Substances

  • Anti-Bacterial Agents
  • RNA, Bacterial
  • bekanamycin
  • Kanamycin