STRUCTURE FUNCTION ANALYSIS OF INTERLEUKIN 7: REQUIREMENT FOR AN AROMATIC RING AT POSITION 143 OF HELIX D

• Published in: Cytokine (Philadelphia, Pa.) Vol. 17; no. 5; pp. 227 - 233
• Main Authors: vanderSpek, Johanna C, Sutherland, John A, Gill, Brian M, Gorgun, Gullu, Foss, Francine M, Murphy, John R
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 07.03.2002
• Subjects: Animals; Binding, Competitive; Cell Line; Dose-Response Relationship, Drug; Electrophoresis, Polyacrylamide Gel; Escherichia coli - metabolism; Histidine - chemistry; Humans; IL-7/mutational analysis; Inhibitory Concentration 50; Interleukin-7 - chemistry; Interleukin-7 - physiology; Mice; Mutagenesis, Site-Directed; Mutation; Phenylalanine - chemistry; Plasmids - metabolism; Proline - chemistry; Protein Binding; Protein Structure, Tertiary; Receptors, Interleukin-7 - chemistry; Receptors, Interleukin-7 - metabolism; Signal Transduction; Tryptophan - chemistry; Tyrosine - chemistry; IL-7/mutational analysis
• ISSN: 1043-4666; 1096-0023
• DOI: 10.1006/cyto.2002.1004

The residues located at the carboxyl terminus of helix D in interleukin-7 (IL-7) have previously been targeted as important for recruitment and binding to the γ chain component of the IL-7 receptor (IL-7R). In this study, Trp 143 of helix D was mutated to His, Phe, Tyr and Pro and these mutants, along with a W143A mutant previously described, were studied to determine the effects on activation of DNA synthesis and binding affinity to IL-7R positive 2E8 cells. The W143F and W143Y mutants were similar to wild type IL-7 in their binding properties and retained 85% and 74% of their activating properties, respectively. In contrast, the W143H mutant possessed a lower binding affinity and a corresponding decrease in activation, the W143A mutant possessed an over 100-fold decreased binding affinity and some residual activation activity and the W143P mutant possessed a greatly decreased binding affinity and did not activate. These results strongly suggest an aromatic residue is required at position 143 for IL-7R binding and subsequent signal transduction.