Plant Type 2B Ca 2+ -ATPases: The Diversity of Isoforms of the Model Plant Arabidopsis thaliana

In plant cells, Ca2+ extrusion from the cytoplasm is accomplished either through Ca2+-H+ antiporters powered by a proton-motive force or through Ca2+ pumps powered by ATP hydrolysis. Plants possess two types of Ca2+-pumping ATPase, named ECAs (for ER-type Ca2+-ATPase) and ACAs (for auto-inhibited Ca2+-ATPase), which group respectively with animal sarco-endoplasmic reticulum Ca2+-ATPase in the 2A subgroup of P-type ATPases or with plasma membrane Ca2+-ATPase in the 2B subgroup. Each type comprises different isoforms, localized on different membranes. Here, we summarize available knowledge of the biochemical characteristics and the physiological role of ACAs, focusing on what we have learnt from analysis of the model plant Arabidopsis thaliana.