SB-219383

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.

SB-219383 and its analogues are a class of potent and specific inhibitors of bacterial tyrosyl-tRNA synthetases. Crystal structures of these inhibitors have been solved in complex with the tyrosyl-tRNA synthetase from Staphylococcus aureus, the bacterium that is largely responsible for hospital-acquired infections. The full-length enzyme yielded crystals that diffracted to 2.8 A resolution, but a truncated version of the enzyme allowed the resolution to be extended to 2.2 A. These inhibitors not only occupy the known substrate binding sites in unique ways, but also reveal a butyl binding pocket. It was reported that the Bacillus stearothermophilus TyrRS T51P mutant has much increased catalytic activity. The S. aureus enzyme happens to have a proline at position 51. Therefore, our structures may contribute to the understanding of the catalytic mechanism and provide the structural basis for designing novel antimicrobial agents.

Carbocyclic analogues of the microbial metabolite SB-219383 have been synthesised and evaluated as inhibitors of bacterial tyrosyl tRNA synthetase. One compound showed highly potent and selective nanomolar inhibition.