3.A.3.7.3
Potassium transporter, KdpABC, with 3 subunits:  KdpA, B2HPR5, 552 aas and 10 TMSs in a 2 + 2 + 2 + 2 + 2 arrangement; KdpB ATPase, B2HRP6, 693 aas and 7  TMSs in a 2 + 2 + 3 TMS arrangement, and KdpC, D2HRP7, 296 aas with one N-terminal TMS and possibly one C-terminal TMS.  A kdpA null mutantion reduced the fraction of persisters after exposure to rifampicin (Liu et al. 2020). kdpA encodes a transmembrane protein that is part of the Kdp-ATPase, an ATP-dependent high-affinity potassium (K⁺) transport system. kdpA expression is induced under low K⁺ conditions and is required for pH homeostasis and growth in media with low concentrations of K⁺. Inactivation of the Kdp system caused hyperpolarization of the membrane potential, increased the proton motive force (PMF) and elevated levels of intracellular ATP. The KdpA mutant phenotype could be complemented with a functional kdpA gene or supplementation with high K⁺ concentrations. Thus, the Kdp system is required for ATP homeostasis and persister formation. ATP-mediated regulation of persister formation may be a general mechanism in bacteria, and suggest that K⁺ transporters may play a role in the regulation of ATP levels and persistence (Liu et al. 2020).