Open AccessPhotoaffinity labeling of ATP and NAD+ binding sites on recombinant human interleukin 2.
Author(s) -
Susan R. Campbell,
Hyun-Tae Kim,
Michael Doukas,
Boyd E. Haley
Publication year - 1990
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.87.3.1243
Subject(s) - lymphokine , nad+ kinase , nucleotide , biochemistry , recombinant dna , chemistry , microbiology and biotechnology , divalent , interleukin 2 , biology , biophysics , stereochemistry , receptor , in vitro , enzyme , organic chemistry , gene
Interleukin 2 (IL-2) is a T-cell-derived lymphokine critical in the activation and proliferation of T cells, B cells, and lymphokine-activated killer cells. It is a glycoprotein of approximately 15,500 daltons that is synthesized and secreted after activation by antigen or mitogen. By using the analogs 8-azidoadenosine 5'-[gamma-32P]triphosphate [( gamma-32P]8N3ATP) and nicotinamide 2-azidoadenine [adenylate-32P]dinucleotide [( alpha-32P]2N3NAD+) as photoaffinity probes, we have detected specific, metal ion-requiring nucleotide binding sites on recombinant human IL-2 (rhIL-2). The specificity of these nucleotide interactions with rhIL-2 was demonstrated by saturation effects and by competition by the parent nucleotides at physiologically relevant concentrations. Saturation of photoinsertion into rhIL-2 occurred at 50 microM [gamma-32P]8N3ATP; a half-maximal decrease of its photoinsertion at 10 microM was obtained with 22 microM ATP. Saturation of photoinsertion with [alpha-32P]2N3NAD+ was observed at 180 microM; a half-maximal decrease of its photoinsertion at 10 microM was effected by 10 microM NAD+ and by 5 microM 3-aminobenzamide. The extent of photoinsertion of both photoprobes into rhIL-2 varied with the presence of different divalent metal ions. rhIL-2 photolabeling with [gamma-32P]8N3ATP appeared to be dependent on the presence of metal ion. It was effectively labeled in the presence of Mg2+ and photoinsertion was increased with the addition of Zn2+ at micromolar concentrations. Also, rhIL-2 underwent slow autophosphorylation by an intramolecular mechanism using [gamma-32P]8N3ATP as well as nonphotoactive nuceotide. The biological significance of these interactions is unknown, but their specificity suggests that nucleotide binding may be involved in the bioactivity of IL-2.