Why are multiple chains required for the interleukin 2 receptor?
The interleukin 2 receptor (IL-2R) is composed of at least two proteins, that is, a 55 kDa L chain (p55, alpha chain) and a 75 kDa H chain (p75, beta chain). The high-affinity binding of IL-2 results in the formation of the ternary complex consisting of IL-2, the L chain and the H chain. Kinetic studies on the IL-2 binding to the high-affinity IL-2R have shown that the association of IL-2 to the L chain is the first step of the ternary complex formation and that expression of a larger number of L chains accelerates the association of IL-2 to the high-affinity IL-2R in agreement with the stepwise binding/affinity conversion model. This conclusion was supported by experiments using several monoclonal antibodies directed to either H or L chain and murine T cell lines which was transfected by the human L chain cDNA. Temperature-sensitive IL-2 binding to the high-affinity receptor is also consistent with the above conclusion. Signal transduction by the IL-2R appears to involve the activation of tyrosine protein kinase. IL-2 signal transduction seems to require the H chain and another yet unidentified molecule, which might have the kinase activity.
Saito
Y
Y
Department of Medical Chemistry, Kyoto University Faculty of Medicine, Japan.
Honjo
T
T
D000818:Animals; D006801:Humans; D007376:Interleukin-2 / Q000493:pharmacokinetics; D008954:Models, Biological; D015394:Molecular Structure; D015375:Receptors, Interleukin-2 / Q000737:chemistry* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology
D007376:Interleukin-2; D015375:Receptors, Interleukin-2