Figure 1.

Illustration of the structure and function of P-class pumps created by authors. (A) SERCA pump transports Ca²⁺ from the cytosol to the lumen. (B) The anti-transportation of 2H⁺ from the cytosol to the lumen and 2K⁺ from the lumen to the cytosol by HKA to regulate intracellular pH. (C) NKA is an anti-porter involved in moving 3 Na⁺ from the cytosol to the ECM for the charge of 2K⁺ being transported into the cytosol. All transportations take place in expense of ATP. ECM, extracellular matrix; SR, sarcoendoplasmic reticulum; SERCA, sarcoendoplasmic reticulum calcium ATPase; HKA, proton potassium ATPase; NKA, sodium potassium ATPase.