IL-2 receptor alpha, soluble

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 extracellular domain, a 19 amino acid transmembrane domain and a 13 amino acid 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 amino acid soluble protein called soluble IL-2R alpha (sIL-2R alpha) . The homodimeric form binds IL-2 (KD=10mM) 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 migrates with an apparent molecular mass of approximately 40-50 kDa by SDS-PAGE gel, under reducing and non-reducing conditions.