- SERCA
SERCA stands for Sarco/Endoplasmic Reticulum Ca2+-
ATPase . It is a P-ATPase of thecalcium ATPase type.Function
SERCA resides in the
sarcoplasmic reticulum (SR) withinmuscle cell s. It is a Ca2+ ATPase which transfers Ca2+ from thecytosol of the cell to the lumen of the SR at the expense ofATP hydrolysis during muscle relaxation.There are 3 major domains on the cytoplasmic face of SERCA: the phosphorylation and nucleotide-binding domains form the catalytic site, whereas the actuator domain is involved in the transmission of major conformational changes.
Regulation
SERCA is normally somewhat inhibited by a protein,
phospholamban , with which it is closely associated.Another protein,calsequestrin , binds calcium within the SR and helps to reduce the concentration of free calcium within the SR, which assists SERCA so that it does not have to pump against such a high concentration gradient. The SR has a much higher concentration of Ca2+ (10,000x) inside when compared to the intracellular Ca2+ concentration.The rate at which SERCA moves Ca2+ across the SR membrane can be controlled by
phospholamban (PLB/PLN) underβ-adrenergic stimulation. When PLB is associated with SERCA, the rate of Ca2+ movement is reduced, upon dissociation of PLB Ca2+ movement increases.Paralogs
There are 3 major
paralogs , SERCA1-3, which are expressed at various levels in different cell types.
* - SERCA1
* - SERCA2
* - SERCA3There are additional post-translational isoforms of both SERCA2 and 3 which serve to introduce the possibility of cell type specific Ca2+-reuptake responses as well as increasing the overall complexity of the Ca2+ signalling mechanism.
External links
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