Calreticulin (human, recombinant; His-tagged)

Calreticulin is a calcium-binding protein involved in intracellular calcium storage and glycoprotein folding, among other processes.^1,2 It is composed of an N-terminal globular N domain, a proline-rich P domain containing a high-affinity, low-capacity calcium-binding site, an acidic C domain containing a low-affinity, high-capacity calcium-binding site, and a C-terminal endoplasmic reticulum retention sequence.³ Calreticulin is widely expressed and localizes primarily to the lumen of the endoplasmic or sarcoplasmic reticulum in non-muscle or muscle cells, respectively, but is also found at the cell surface, in the extracellular matrix, and in the cytoplasm.^3,4,1 It has a high calcium-binding capacity and is involved in the regulation of intracellular calcium homeostasis, which makes it an integral factor in many calcium-related processes, such as muscle contraction and the cellular stress response.^3,4 Calreticulin also acts as a chaperone for newly synthesized glycoproteins in conjunction with protein disulfide-isomerase A3, also known as ERp57, and calnexin in the calreticulin/calnexin cycle to ensure proper glycoprotein folding.¹ Insertion or deletion mutations in exon 9 of CALR, the gene encoding calreticulin, are found in a subset of patients with essential thrombocythemia or primary myelofibrosis and are associated with increased overall survival and a lower risk of thrombosis.⁵ Cayman's Calreticulin (human, recombinant; His-tagged) protein consists of 407 amino acids, has a calculated molecular weight of 47.4 kDa, and a predicted N-terminus of Glu18 after signal peptide cleavage. By SDS-PAGE, under reducing conditions, the apparent molecular mass of the protein is 58 kDa due to glycosylation.

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1. Wang, Q., Groenendyk, J., and Michalak, M. Glycoprotein quality control and endoplasmic reticulum stress. Molecules 20(8), 13689-13704 (2015).

2. Gold, L.I., Eggleton, P., Sweetwyne, M.T., et al. Calreticulin: Non-endoplasmic reticulum functions in physiology and disease. FASEB J. 24(3), 665-683 (2010).

3. Michalak, M., Milner, R.E., Burns, K., et al. Calreticulin. Biochem J. 285(Pt 3), 681-692 (1992).

4. Wang, W.-A., Groenendyk, J., and Michalak, M. Calreticulin signaling in health and disease. Int. J. Biochem. Cell Biol. 44(6), 842-846 (2012).

5. Klampfl, T., Gisslinger, H., Harutyunyan, A.S., et al. Somatic mutations of calreticulin in myeloproliferative neoplasms. N. Engl. J. Med. 369(25), 2379-2390 (2013).