Description
The IL-2 receptor system consists of three non-covalently linked subunits termed IL-2R alpha, IL- 2R beta, and IL-2R gamma. The IL-2R alpha is a type I transmembrane protein consisting of a 219 amino acid (a.a.) extracellular domain, a 19 a.a. transmembrane domain and a 13 a.a. intracellular domain, which is not involved in the transduction of IL-2 signals. Proteolytic processing of IL-2R alpha releases the entire extracellular domain of IL-2R alpha thereby generating a 219 a.a. soluble protein called soluble IL-2R alpha (sIL-2R alpha). The homodimeric form binds IL-2 (KD=10 mM) and facilitates IL-2 signaling. The secreted sIL-2R alpha is expressed on leukemia cells, lymphoma cells, newly activated T and B cells, as well as on approximately 10% of NK cells. Recombinant human sIL-2R alpha is a 24.8 kDa protein containing 219 amino acid residues consisting of only the extracellular domain of IL-2R-alpha. Due to glycosylation, IL-2R-alpha has an approximate molecular weight of 31 kDa based on SDS-PAGE gel and mass spectrometry