Structural analysis of recombinant soluble human interleukin-2 receptor. Primary structure, assignment of disulfide bonds and core IL-2 binding structure.

A purified soluble and functional form of recombinant human interleukin-2 receptor, engineered and expressed in Chinese hamster ovary cells, was structurally characterized. The primary sequence of this 224 amino acid recombinant protein which lacks most of the carboxy-terminal transmembrane and cytoplasmic portions of the intact protein was established by sequence analyses. The disulfide bonds were assigned by comparative peptide mapping of the reduced and non-reduced peptide digests. As in the case of natural interleukin-2 receptor they occur between cysteines 3-147, 46-104, 131-163, and 28/30-59/61. Based on assignment of the disulfide bonds, a structural model of the interleukin-2 receptor for interleukin-2 binding is proposed.