Structural and biochemical characterization of Aminoglycoside-O-nucleotidyltransferase-6Ib from Campylobacter fetus | Poster Board #183

Antibiotic drugs have served as essential tools in the treatment of serious bacterial infections since the 1940s and have since revolutionized modern medicine. Aminoglycosides are a class of antibiotics that function by causing translational miscoding during protein synthesis in bacteria. However, the overuse of these drugs has led to a rise in antibiotic resistance severely reducing their efficacy. The most common form of resistance to these drugs is their inactivation by several diverse families of bacterial antibiotic modifying enzymes (AMEs). The AME aminoglycoside nucleotidyltransferase(6)-Ib (ANT(6)-Ib) catalyzes the addition of an adenyl group to position 6 on the antibiotic streptomycin. This modification alters the structure of the drug, thereby hindering its ability to bind to its target, the bacterial ribosome. Despite the significance of this enzymatic activity, ANT(6)-Ib has not been well studied. Here, we used cellular growth assays and steady-state kinetics to biochemically characterized the activity of the ANT(6)-Ib enzyme from Campylobacter fetus subsp fetus. Furthermore, we determined the high-resolution crystal structure of the streptomycin bound enzyme. Using these data, we identified key amino acid residues involved in substrate binding and catalysis. These data provide valuable insights into the molecular mechanism of the ANT(6) enzyme family that will be critical to the future development of inhibitory strategies to overcome ANT induced antibiotic resistance.