The human intermediate‐affinity interleukin 2 receptor consists of two distinct, partially homologous glycoproteins

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Abstract
In this report we demonstrate that the human intermediate‐affinity‐type interleukin (IL)2 receptor (IL2R) consists of two distinct glycoproteins designated H1 and H2, whereas the high‐affinity IL2R consists of three chains, H1, H2 and the light chain (L), the Tac antigen. They are neither linked by disulfide bridges to each other nor to the L chain. Similar to the L chain, H1 and H2 apparently carry intramolecular disulfide bonds. From affinity‐labeled IL2 intermediate‐affinity receptor complexes, we deduced an apparent mol. mass of 70 kDa for H1 and of 75 kDa for H2 in sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and of 55 kDa for H1 and of 85 kDa for H2 in SDS‐PAGE/urea. As demonstrated by limiting proteolysis, both glycoproteins display high homologies or even identity proximal to the IL2‐binding sites. The areas which are responsible for the striking differences between H1 and H2 in SDS‐PAGE/urea are located distally to the IL2‐binding site and, in contrast to the L chain, are protected from the action of exogenous proteases by the plasma membrane.
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