Multiple amino acid substitutions suggest a structural basis for the separation of biological activity and receptor binding in a mutant interleukin-1 beta protein.
Receptor binding and biological activity properties of human interleukin-1 beta can be dissociated by mutating a single amino acid, arginine 127, to glycine (IL-1 beta R----G) [Gehrke et al. (1990) J. Biol. Chem. 265, 5922-5925]. The mechanism underlying the reduced biological activity has been examined by replacing arginine 127 with several other amino acids, followed by determination of biological activity using a T-helper cell proliferation assay. Mutant IL-1 beta proteins containing lysine, glutamic acid, tryptophan, or alanine in place of arginine 127 maintain biological activity. These data strongly suggest that IL-1 beta biological activity is not directly dependent upon the specific properties of charge, hydrophobicity/hydrophilicity, or side-chain group presented by the residue at position 127. Molecular modeling analyses indicate that the structural integrity of the antiparallel beta-strand 1/12 pair is disturbed in the glycine 127 mutant protein. Collapse of beta-strand 1 into a hydrated space between strands 1, 2, and 4 could structurally alter a cleft in IL-1 beta that contains a cluster of highly conserved amino acids, including a key aspartic acid residue [Ju et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 2658-2662]. Mutagenesis data and the differential activities of the IL-1 beta R----G and IL-1 receptor antagonist proteins in stimulating early and late gene expression [Conca et al. (1991) J. Biol. Chem. 266, 16265-16268] suggest that multiple receptor-ligand contacts, exclusive of those required for receptor binding, are required for the stimulation of full IL-1 biological activity.
Auron
P E
PE
Department of Pathology, Harvard Medical School, Boston, Massachusetts 02114.
Quigley
G J
GJ
Rosenwasser
L J
LJ
Gehrke
L
L
D000595:Amino Acid Sequence; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011971:Receptors, Immunologic / Q000378:metabolism*; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D006377:T-Lymphocytes, Helper-Inducer / Q000187:drug effects / Q000276:immunology*; D014961:X-Ray Diffraction
D007375:Interleukin-1; D046911:Macromolecular Substances; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins