Structure-function analysis of human interleukin-2. Identification of amino acid residues required for biological activity.
To locate functional domains of the interleukin-2 (IL-2) protein, a cDNA clone encoding biologically active human IL-2 was mutagenized using synthetic oligonucleotides to incorporate defined amino acid substitutions and deletions in the mature protein. The IL-2 analogs were then produced in Escherichia coli and assayed for the ability to induce proliferation of IL-2-dependent cells and the ability to compete for binding to the IL-2 receptor. Our analysis of over 50 different mutations demonstrated that the integrity of at least three regions of the IL-2 molecule is required for full biological activity: the NH2 terminus (residues 1-20), the COOH terminus (residues 121-133), and 2 of the 3 cysteine residues (58 and 105). Deletion of the NH2-terminal 20 amino acids or the COOH-terminal 10 amino acids resulted in the loss of greater than 99% of bioactivity and binding. Amino acid substitutions at specific positions in these regions also resulted in proteins which retained less than 1% activity. The NH2 terminus and an adjacent internal region were recognized by neutralizing anti-IL-2 antibodies. In combination with the results from epitope competition analysis with neutralizing antibodies, these data are consistent with the IL-2 protein being folded such that the NH2 terminus, the COOH terminus, and the internal 30- to 60-region are juxtaposed to form the binding site recognized by the IL-2 receptor.
D000595:Amino Acid Sequence; D001483:Base Sequence; D004247:DNA / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics* / Q000502:physiology; D009154:Mutation; D010957:Plasmids; D011971:Receptors, Immunologic / Q000378:metabolism; D015375:Receptors, Interleukin-2; D013329:Structure-Activity Relationship
D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D004247:DNA