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Receptor epitope usage by an interleukin-5 mimetic peptide
Tetsuya Ishino1, Cecilia Urbina, Madhushree Bhattacharya
1Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA.
The Journal of Biological Chemistry
|April 14, 2005
Summary
The cyclic peptide AF17121 inhibits interleukin-5 (IL5) activity by binding to the IL5 receptor alpha (IL5Ralpha). This peptide shares binding sites with IL5, revealing key receptor residues involved in the interaction.
Area of Science:
- Biochemistry
- Immunology
- Molecular Biology
Background:
- The cyclic peptide AF17121 is a known antagonist of human interleukin-5 (IL5) receptor alpha (IL5Ralpha).
- Previous studies identified critical arginine and acidic residues in AF17121 for its inhibitory effect.
- The precise mechanism of IL5Ralpha recognition by AF17121 remained unclear.
Purpose of the Study:
- To elucidate the binding mechanism of AF17121 to IL5Ralpha.
- To identify the specific amino acid residues on IL5Ralpha involved in AF17121 binding.
- To compare the binding interaction of AF17121 with that of IL5.
Main Methods:
- Recombinant DNA techniques were used to create a fusion peptide of AF17121 and thioredoxin.
- Surface plasmon resonance biosensor was employed to analyze the kinetics of AF17121-IL5Ralpha interaction.
- Alanine substitution was performed on specific IL5Ralpha residues (Asp55, Asp56, Glu58, Lys186, Arg188, Arg297) to define the binding footprint.
Main Results:
- Kinetic analysis showed comparable dissociation rates between the AF17121-IL5Ralpha and IL5-IL5Ralpha complexes.
- The fusion peptide competed with IL5 for binding to IL5Ralpha, indicating shared binding sites.
- Alanine substitutions revealed that Asp55, Arg188, and Arg297 in the fibronectin type III domains D1, D2, and D3, respectively, are crucial for AF17121 interaction.
Conclusions:
- AF17121 binds to IL5Ralpha at sites overlapping with IL5 binding.
- The binding footprint of AF17121 on IL5Ralpha is a subset of the IL5 binding site.
- These findings provide insights into how AF17121 antagonizes IL5 signaling by mimicking IL5 binding but blocking receptor activation.