Receptor-binding conformation of the “ELR” motif of IL-8: X-ray structure of the L5C/H33C variant at 2.35 Å resolution

✍ Scribed by Nancy Gerber; Henry Lowman; Dean R. Artis; Charles Eigenbrot

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 497 KB
• Volume: 38
• Category: Article
• ISSN: 0887-3585
• DOI: 10.1002/(sici)1097-0134(20000301)38:4<361::aid-prot2>3.0.co;2-0

✦ Synopsis

The "ELR" (Glu-Leu-Arg) tripeptide sequence near the N-terminus of interleukin-8 (IL-8) contributes a large part of the receptor binding free energy. Prior X-ray and nuclear magnetic resonance (NMR) structures of IL-8 have shown this region of the molecule to be highly mobile. We reasoned that a hydrophobic interaction between the leucine and the neighboring ␤-turn might exist in the receptor binding conformation of the Nterminus. To test this hypothesis, we mutated two residues to cysteine and connected the N-terminus to the ␤-turn. The mutant retains receptor binding affinity reasonably close to wild type and allows the characterization of a high-affinity conformation that may be useful in the design of small IL-8 mimics. The L5C/H33C mutant is refined to R-values of R ‫؍‬ 20.6% and R free ‫؍‬ 27.7% at 2.35 Å resolution. Other receptor binding determinants reside in the "N-loop" found after "ELR" and preceding the first ␤-strand. All available structures of IL-8 have been found with one of two distinct N-loop conformations. One of these is relevant for receptor binding, based on NMR results with receptor peptides. The other conformation obscures the receptor-peptide binding surface and may have an undetermined but necessarily different function.