Calsequestrin
| Calsequestrin-1 | ||
|---|---|---|
|
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| Ribbon / surface model of calsequestrin-1 from fast-contracting skeletal muscle fibers of the wild rabbit ( Oryctolagus cuniculus ) according to PDB 1A8Y | ||
| Properties of human protein | ||
| Mass / length primary structure | 362 amino acids | |
| Identifier | ||
| Gene name | CASQ1 | |
| External IDs | ||
| Occurrence | ||
| Homology family | Calsequestrin | |
| Parent taxon | Euteleostomi | |
Calsequestrin is a calcium- binding protein in muscle cells of vertebrates . It is found there in the terminal cisterns of the sarcoplasmic reticulum (SR). It can bind 65 Ca 2+ ions per molecule with low affinity. The storage capacity ensures that Ca 2+ is present in high concentrations in the muscle, but can also be released again quickly due to the weak bond. Binding to calsequestrin removes the ions from equilibrium. The SR's Ca 2+ pumps therefore have to work against a lower concentration gradient, which is how the 1000 times higher calcium ion concentration in the cistern is made possible in the first place.
The slightly modified isoform of calsequestrin-1 that occurs in the heart muscle is called calsequestrin-2. Mutations in its gene (CASQ2) can cause hereditary ventricular tachycardia .
Calsequestrin in muscle cells in the swordfish eye
The muscle cells of the rebuilt eye muscle, the rectus superior muscle, do not have calcium- binding proteins such as troponin or calmodulin , actin and myosin . Here, as in other cells, ATP is formed in the mitochondria . When the cell is excited by the motor endplate, calcium is released from the sarcoplasmic reticulum. The increase in calcium concentration promotes ATP formation in the mitochondrion. With ATP consumption, the calcium is pumped back into the SR by the calsequestrin. The work done leads to heat generation . This allows the swordfish to control its intercranial temperature independently of the cold surrounding water. In addition, there is a miracle net , which, thanks to its counter-current principle, ensures that the heat stays in the desired area.
literature
- Jeremy M. Berg, John L. Tymoczko, Lubert Stryer : Biochemistry. 6 edition, Spektrum Akademischer Verlag, Heidelberg 2007. ISBN 978-3-8274-1800-5 .
- Donald Voet, Judith G. Voet: Biochemistry. 3rd edition, John Wiley & Sons, New York 2004. ISBN 0-471-19350-X .
- Bruce Alberts , Alexander Johnson, Peter Walter, Julian Lewis, Martin Raff, Keith Roberts: Molecular Biology of the Cell , 5th Edition, Taylor & Francis 2007, ISBN 978-0-8153-4106-2 .