IL-2 R beta is a member of the cytokine receptor superfamily. Human IL-2 R beta cDNA encodes a 551 amino acid residue precursor Type I membrane protein with a 26 residue signal peptide, a 214 residue extracellular region, a 25 residue transmembrane region and a 286 residue cytoplasmic domain. Functional IL-2 receptors can exist in two affinity states on cell surfaces, the high affinity complex consisting of heterotrimers of the alpha, beta, and gamma chains, and the intermediate affinity complex comprising heterodimers of the beta and gamma chains.

> 95% as determined by Tris-Bis PAGE; ; > 90% as determined by HPLC