ABSTRACT
The compound designated SB-219383 is a potent and selective inhibitor of bacterial tyrosyl tRNA synthetases. It exhibits an IC50 of < 1 nM against Staphylococcus aureus tyrosyl tRNA synthetase and weak in vitro activity against Staphylococci and Streptococci. Here we present data consistent with SB-219383 eliciting an amino acid starvation in both S. aureus and Streptococcus pneumoniae, supporting the conclusion that the antibacterial activity of SB-219383 is due to tyrosyl tRNA synthetase inhibition.
Subject(s)
Bridged Bicyclo Compounds, Heterocyclic/pharmacology , Enzyme Inhibitors/pharmacology , Furans/pharmacology , Micromonospora/metabolism , Staphylococcus aureus/drug effects , Streptococcus pneumoniae/drug effects , Tyrosine-tRNA Ligase/antagonists & inhibitors , Culture Media , Guanosine Tetraphosphate/metabolism , Leucine/metabolism , Staphylococcus aureus/enzymology , Staphylococcus aureus/growth & development , Streptococcus pneumoniae/enzymology , Streptococcus pneumoniae/growth & development , Uridine/metabolismABSTRACT
In an assessment of antibiotic action on Staphylococcus aureus, we found that distinct changes in intracellular nucleotide pools occur depending on the antibiotic mode of action. In particular, we have quantitated the effect of antibiotics on pools of the nucleotide guanosine 3'-diphosphate, 5'-triphosphate (pppGpp). Intracellular pppGpp levels increased in response to treatment with the isoleucyl tRNA synthetase inhibitor mupirocin, the uncoupler carbonyl cyanide-m-chlorophenylhydrazone, and rifampicin. These compounds were distinguishable by the degree in which they increased the pppGpp pool and by their differential effect on the pools of other nucleotides. This technique has been used to confirm and to refute the expected mode of action of several compounds identified as possible inhibitors of tRNA synthetases. Our results provide the framework for using nucleotide analysis in the assessment of novel antimicrobial compounds with unknown modes of action.
