The gamma chain of the high affinity functional human IL-2 receptor complex belongs to the hematopoietin receptor family. IL-2 R gamma is a 369 amino acid residue protein consisting of a 22 residue signal sequence, a 232 residue extracellular domain, a 29 residue transmembrane domain and an 86 residue cytoplasmic domain. Although IL-2 R gamma by itself does not bind IL-2 with any appreciable affinity, it is required for IL-2 receptor signaling.