title: Structure function analysis of interleukin 7: requirement for an aromatic ring at position 143 of helix D.
abstract: 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 gamma 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.
authors.affiliation: Evans Department of Clinical Research and the Department of Medicine, Boston Medical Center, Boston, Massachusetts, 02118, USA. johanna.vanderspek@bmc.org
authors.forename: Johanna C
authors.initials: JC
authors.lastname: vanderSpek
authors.forename: John A
authors.initials: JA
authors.lastname: Sutherland
authors.forename: Brian M
authors.initials: BM
authors.lastname: Gill
authors.forename: Gullu
authors.initials: G
authors.lastname: Gorgun
authors.forename: Francine M
authors.initials: FM
authors.lastname: Foss
authors.forename: John R
authors.initials: JR
authors.lastname: Murphy
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D006801:Humans; D020128:Inhibitory Concentration 50; D015851:Interleukin-7 / Q000737:chemistry* / Q000502:physiology*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010649:Phenylalanine / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020395:Receptors, Interleukin-7 / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
chemical_list: D015851:Interleukin-7; D020395:Receptors, Interleukin-7; D014443:Tyrosine; D010649:Phenylalanine; D006639:Histidine; D014364:Tryptophan; D011392:Proline