Characterization of VraS Kinase Involved in Bacterial Resistance

Staphylococcus aureus bacteria utilizes VraS histidine kinase to receive and relay environmental stress signals. VraS is highly implicated in the development of bacterial resistance as it upregulates cell wall synthesis after exposure to antibiotics. Thus, VraS constitutes an attractive target in drug discovery as its inhibition can extend or restore the efficacy of many safe antibiotics. Characterization of the enzymatic activity of VraS was conducted to understand the factors that contribute to its activity. VraS was expressed in BL21 and purified using affinity chromatography techniques. Activity was characterized using a coupled assay to determine the kinetics of the kinase autophosphorylation reaction. The rate of the reaction increases with increasing enzyme concentration (1 – 4 µM) and with temperature (22, 25, 37 °C). The enzyme is active only in presence of Mg2+ but not Mn2+. The Km of ATP was 20 µM for the autophosphorylation reaction.