Low-affinity potassium transport system. Interacts with Trk system potassium uptake protein TrkA. Requires TrkE (sapD) for maximal transport activity, low activity is seen in its absence; no further stimulation is seen with SapF (PubMed:11700350). Transport in the absence of SapD is dependent on a high membrane potential and a high cytoplasmic ATP concentration, suggesting this protein may be able to interact with other ATP-binding proteins (PubMed:11700350). Can transport potassium and rubidium (PubMed:7896723). Belongs to the TrkH potassium transport family.