Part of the high-affinity ATP-driven potassium transport (or Kdp) system, which catalyzes the hydrolysis of ATP coupled with the electrogenic transport of potassium into the cytoplasm (PubMed:2849541, PubMed:8499455, PubMed:23930894). This subunit acts as a catalytic chaperone that increases the ATP-binding affinity of the ATP-hydrolyzing subunit KdpB by the formation of a transient KdpB/KdpC/ATP ternary complex (PubMed:21711450). The system is composed of three essential subunits: KdpA, KdpB and KdpC (PubMed:2849541, PubMed:9858692, PubMed:28636601, PubMed:30478378). The complex also contains KdpF, a small non-essential subunit (PubMed:10608856, PubMed:28636601, PubMed:30478378). The KdpFABC complex exists as a dimer above concentrations of 30-50 nM, whereas the complex exists as a functional monomer at lower concentrations (PubMed:18298081). Transcriptionally regulated by the KdpD/KdpE two-component regulatory system. Belongs to the KdpC family.