Module 5: Figure Ca2+ uptake and extrusion
Functional organization of Ca2+ pumps.
The Na+/Ca2+ exchanger (NCX) and the mitochondrial uniporter are particularly effective at pumping Ca2+ when the cytosolic Ca2+ concentration is high, in that they combine a low affinity for Ca2+ with a high capacity. The plasma membrane Ca2+-ATPase (PMCA) and sarco/endo-plasmic reticulum Ca2+-ATPase (SERCA) pumps have much lower capacities, but their much higher affinities enable them to reduce the level of Ca2+ back to its resting level. The different extrusion mechanisms thus co-operate with each other to regulate the level of Ca2+ over a large dynamic range.