Sandbox Reserved 820

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This Sandbox is Reserved from 06/12/2018, through 30/06/2019 for use in the course "Structural Biology" taught by Bruno Kieffer at the University of Strasbourg, ESBS. This reservation includes Sandbox Reserved 1480 through Sandbox Reserved 1543.
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Crystal Structure of Human Cardiac Calsequestrin, (PDB code 2vaf)

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Calsequestrin-2 (or CASQ2) is the soluble Ca2+ binding protein in the sarcoplasmic reticulum lumen of the cardiac muscle cells. CASQ2 could be either in a monomeric, homodimeric, or homooligomeric chain form depending on its bounds with Ca2+. Mutations of CASQ2 are involved in cardiac diseases such as Catecholaminergic Polymorphic Ventricular Tachycardia.

Calsequestrin in the calcium cycle of myocyte contraction
Calsequestrin in the calcium cycle of myocyte contraction

Biological role

The contractions of cardiac myocytes are triggered by the increase of calcium concentration in the cytosol. This phenomenon is highly controlled at several levels. First the calcium is stocked in a cell compartment called the sarcoplasmic reticulum. Then the release of calcium in the cytosol is dependent of the myocytes membrane depolarization. Finally the release of calcium is extremely brief, as soon as the depolarization is over, the calcium is actively pumped in the sarcoplasmic reticulum.

The calsequestrin 2 plays a major role here, because it helps the release of the calcium in the cytosol while the membrane depolarization occurs and traps the calcium inside the lumen of the sarcoplasmic reticulum. It is also good to notice that a huge release of calcium in the cytosol would be lethal to the cell, since the calcium would precipitate with the free phosphate groups.


Structure

General Structure

There are and . can bind the Ca2+ especially the and the .

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