The P-type pumps or P-type ATPases are a type of ATP-driven membrane transporters. One of the most common examples of P-type pumps are the sarco/endoplasmic reticulum Ca-ATPase or SERCA present on the sarcoplasmic reticulum or SR membrane in the skeletal muscles. The pump has a transmembrane domain and a cytoplasmic headpiece consisting of three domains: N, nucleotide-binding, P, phosphorylation, and A, actuator. ATP is bound to the N-domain of the pump. Then, two calcium ions from the cytosolic side bind to the calcium-binding site present within the membrane-spanning domain. The ATP is then hydrolyzed to ADP and inorganic phosphate. The inorganic phosphate attaches to the P-domain. The ADP dissociates, followed by binding a new ATP molecule triggering a conformational change in the pump that opens the passageway to the SR lumen and releases the calcium ions. Two hydrogen ions from the SR lumen bind to the empty calcium-binding sites closing the passageway to the lumen. After this, the inorganic phosphate from the P-domain dissociates. The hydrogen ions temporarily bound to the calcium-binding sites are released, and the pump returns to its initial conformation.