A high-throughput screen of the GTPase activity of Escherichia coli EngA to find an inhibitor of bacterial ribosome biogenesis

Abstract

<p>The synthesis of ribosomes is an essential process, which is aided by a variety of transacting factors in bacteria. Among these is a group of GTPases essential for bacterial viability and emerging as promising targets for new antibacterial agents. Herein, we describe a robust high-throughput screening process for inhibitors of one such GTPase, the Escherichia coli EngA protein. The primary screen employed an assay of phosphate production in 384-well density.<br />Reaction conditions were chosen to maximize sensitivity for the discovery of competitive inhibitors while maintaining a strong signal amplitude and low noise. In a pilot screen of 31,800 chemical compounds, 44 active compounds were identified. Further, we describe the elimination of non-specific inhibitors that were detergent-sensitive or reactive as well as those that interfered with the high-throughput phosphate assay. Four inhibitors survived these common counterscreens for non-specificity but these chemicals were also inhibitors of the unrelated enzyme dihydrofolate reductase, suggesting that they too were promiscuously active. The highthroughput screen of the EngA protein described here provides a meticulous pilot study in the search for specific inhibitors of GTPases involved in ribosome biogenesis.</p>