Member of the two-component regulatory system YpdA/YpdB, which is part of a nutrient-sensing regulatory network composed of YpdA/YpdB, the high-affinity pyruvate signaling system BtsS/BtsR and their respective target proteins, YhjX and BtsT. YpdA activates YpdB by phosphorylation in response to high concentrations of extracellular pyruvate. Activation of the YpdA/YpdB signaling cascade also promotes BtsS/BtsR-mediated btsT expression. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Interacts with BtsT and YhjX. Autophosphorylated.