Investigating the Molecular Mechanism and Function of the Histidine Kinase TrcS in <i>Mycobacterium tuberculosis</i>

<i>Mycobacterium tuberculosis</i> (<i>Mtb</i>) is a critical intracellular pathogen responsible for tuberculosis (TB), a highly detrimental infectious disease. For survival in the changing host environment, <i>Mtb</i> employs two-component systems to regulate gene expression and control protein production. Among these systems, histidine kinase TrcS plays a key role in this adaptive response. However, the functional mechanism of <i>Mtb</i> TrcS remains unknown. Here, we successfully obtained monomeric TrcS. G254D or G254R significantly decreased the histidine kinase activity of TrcS compared with the wild-type protein, whereas A220 V or A220I caused a slight decrease in the activity. Gene <i>TrcS</i> induced upregulation of <i>MtrA</i>/<i>B</i> transcript levels in WT and ΔtrcS::trcS <i>Mtb</i>, but downregulation in ΔtrcS <i>Mtb</i>. Deletion of the gene <i>TrcS</i> increased the virulence of <i>Mtb</i>. Our findings contribute to a deeper understanding of the functionality of <i>Mtb</i> TrcS and provide foundational insights for the future development of novel antituberculosis drugs.