Calsequestrin

• OMIM: 114 250
• UniProt: P31415

Calsequestrin is a calcium -binding protein in muscle cells of vertebrates. It is found there in the terminal cisternae of the sarcoplasmic reticulum (SR ). Per molecule can bind 65 Ca 2 ions with low affinity. The storage capacity ensures that Ca2 is present in muscle in high concentrations, but can also be quickly released again because of weak binding. By binding to the Calsequestrin ions are removed from the equilibrium. The Ca2 pump of the SR must thus work against a lesser concentration, the thousand-fold higher calcium ion concentration in the cistern is at all possible.

The in cardiac muscle occurring, slightly modified isoform of calsequestrin -1 is called calsequestrin -2. Mutations in the gene ( CASQ2 ) can cause hereditary ventricular tachycardia.

Calsequestrin in muscle cells in the eye of the swordfish

The muscle cells of the converted eye muscle, superior rectus, do not have calcium-binding proteins such as troponin and calmodulin, actin and myosin. Here as well, ATP formed in different cells in the mitochondria. Upon excitation of the cell, through the motor end plate, calcium is released from the sarcoplasmic reticulum. The increase in calcium concentration promotes the formation of ATP in the mitochondrion. Consumption of ATP from the calcium is pumped back into the SR calsequestrin. The work done in this case leads to heat buildup. This allows the swordfish control his intracranial temperature regardless of the cold surrounding water. In addition, here's another miracle network, which ensures by its counter-current principle that the heat stays in the desired area.