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Analysis of IL-2 functional structure by multiple cysteine substitutions.
1Division of Cytokine Biology, Food and Drug Administration, Bethesda, MD 20892.
Biochemical and Biophysical Research Communications
|October 30, 1992
Summary
Interleukin-2 (IL-2) activity is significantly impacted by its disulfide bonds. Incorrect disulfide bond formation in IL-2 muteins drastically reduces their potency and receptor binding affinity.
Area of Science:
- Biochemistry
- Molecular Biology
- Immunology
Background:
- Interleukin-2 (IL-2) is a critical cytokine for immune cell proliferation.
- IL-2 possesses three cysteine residues, with Cys58 and Cys105 forming a crucial intramolecular disulfide bond in the active form.
Purpose of the Study:
- To investigate the functional significance of correct disulfide bond formation in IL-2.
- To characterize the activity and receptor binding of IL-2 muteins with altered cysteine residues.
Main Methods:
- Site-directed mutagenesis using polymerase chain reaction to create IL-2 muteins (A58/105/125 and A58/125).
- Thymidine incorporation assays using CTLL-2 cells to assess biological activity.
- Binding inhibition studies to evaluate receptor affinity.
Main Results:
- IL-2 muteins A58/105/125 and A58/125 exhibited significantly reduced potency (0.5-2.0% of wild-type IL-2).
- These muteins were 50-200 fold more active than the A58 mutein.
- Muteins A58/125 and A58/105/125 showed 5-25 fold higher relative affinity for high-affinity IL-2 receptors compared to A58.
Conclusions:
- The dramatic loss of activity in mutein A58 is likely due to the formation of an incorrect disulfide bond between Cys105 and Cys125.
- Correct disulfide bond formation is essential for maintaining the full biological activity and receptor binding of Interleukin-2.