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 molecu ...
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 beta-turn might exist in the receptor binding conformation of the N-terminus. To test this hypothesis, we mutated two residues to cysteine and connected the N-terminus to the beta-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 Rfree = 27.7% at 2.35 A resolution. Other receptor binding determinants reside in the "N-loop" found after "ELR" and preceding the first beta-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.
Related Citations:
Crystal structure of IL-8:Symbiosis of NMR and crystallography Baldwin, E.T., Weber, I.T., Charles, R.St., Xuan, J.-C. (1991) Proc Natl Acad Sci U S A 88: 502
Structural change and receptor binding in a chemokine mutant with a re- arranged disulfide: X-ray structure of E38C/C50A IL-8 at 2 A resolution. Eigenbrot, C., Lowman, H.B., Chee, L., Artis, D.R. (1997) Proteins 27: 556
Organizational Affiliation:
Department of Protein Engineering Genentech, Inc., South San Francisco, California, USA.
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