Localization in human interleukin 2 of the binding site to the alpha chain (p55) of the interleukin 2 receptor.
Human interleukin 2 (IL-2) analogs with defined amino acid substitutions were used to identify specific residues that interact with the 55-kDa subunit (p55) or alpha chain of the human IL-2 receptor. Analog proteins containing specific substitutions for Lys-35, Arg-38, Phe-42, or Lys-43 were inactive in competitive binding assays for p55. All of these analogs retained substantial competitive binding to the intermediate-affinity p70 subunit (beta chain) of the receptor complex. The analogs varied in ability to interact with the high-affinity p55/p70 receptor. Despite the lack of binding to p55, all analogs exhibited significant biological activity, as assayed on the murine CTLL cell line. The dissociation constants of Arg-38 and Phe-42 analogs for p70 were consistent with intermediate-affinity binding; the Kd values were not significantly affected by the presence of p55 in binding to the high-affinity IL-2 receptor complex. These results confirm the importance of the B alpha-helix in IL-2 as the locus for p55-receptor binding and support a revised model of IL-2-IL-2 receptor interaction.
Sauvé
K
K
Department of Molecular Genetics, Roche Research Center, Hoffmann-La Roche Inc., Nutley, NJ 07110.
Nachman
M
M
Spence
C
C
Bailon
P
P
Campbell
E
E
Tsien
W H
WH
Kondas
J A
JA
Hakimi
J
J
Ju
G
G
D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
D007376:Interleukin-2; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins