SERCA

SERCA, or sarco/endoplasmic reticulum Ca²⁺-ATPase, or SR Ca²⁺-ATPase, is a calcium ATPase-type P-ATPase.

Function

SERCA resides in the sarcoplasmic reticulum (SR) within muscle cells. It is a Ca²⁺ ATPase that transfers Ca²⁺ from the cytosol of the cell to the lumen of the SR at the expense of ATP hydrolysis during muscle relaxation.

There are 3 major domains on the cytoplasmic face of SERCA: the phosphorylation and nucleotide-binding domains, which form the catalytic site, and the actuator domain, which is involved in the transmission of major conformational changes.

It seems that, in addition to the calcium-transporting properties, SERCA1 generates heat in some adipocytes and can improve cold tolerance in some wood frog.

Regulation

The rate at which SERCA moves Ca²⁺ across the SR membrane can be controlled by the regulatory protein phospholamban (PLB/PLN). SERCA is normally inhibited by PLB, with which it is closely associated. Increased β-adrenergic stimulation reduces the association between SERCA and PLB by the phosphorylation of PLB by PKA. When PLB is associated with SERCA, the rate of Ca²⁺ movement is reduced; upon dissociation of PLB, Ca²⁺ movement increases.