This model describes the P-type ATPase responsible for translocating calcium ions across the plasma membrane of eukaryotes, out of the cell. In some organisms, this type of pump may also be found in vacuolar membranes. In humans and mice, at least, there are multiple isoforms of the PMCA pump with overlapping but not redundant functions. Accordingly, there are no human diseases linked to PMCA defects, although alterations of PMCA function do elicit physiological effects. The calcium P-type ATPases have been characterized as Type IIB based on a phylogenetic analysis which distinguishes this group from the Type IIA SERCA calcium pump. A separate analysis divides Type IIA into sub-types (SERCA and PMR1) which are represented by two corresponding models (TIGR01116 and TIGR01522). This model is well separated from those.