Importance of the loop connecting A and B helices of human interferon-gamma in recognition by interferon-gamma receptor.
Characterization of murine-human hybrid interferon-gamma (IFN-gamma) molecules suggests that substitution of the peptide connecting the A and B helices in human IFN-gamma with the murine sequence significantly blocks the protein's binding to the human interferon-gamma receptor. Mutagenesis showed that this effect is localized to the central part of this A-B loop peptide, particularly Ser20, Asp21, Val22, and Ala23. One mutant, IFN-gamma/A23E,D24E,N25K, was examined by NMR. This "EEK" mutation does not significantly alter the conformation of interferon-gamma, suggesting that the effects of these mutations are not the result of global conformational changes. The A-B loop is near histidine 111, a residue previously shown to be important in receptor-ligand interaction (Lunn, C. A., Fossetta, J., Dalgarno, D., Murgolo, N., Windsor, W., Zavodny, P. J., Narula, S. K., and Lundell, D. (1992) Protein Eng. 5, 253-257). We show that copper forms a complex between histidine 19 in the A-B loop and histidine 111. This metal complex lacks the ability to interact with the interferon-gamma receptor. These results suggest that the A-B loop contains important structural information needed for receptor-ligand binding and hence biological activity of human interferon-gamma.
Lundell
D
D
Department of Immunology, Schering-Plough Research Institute, Kenilworth, New Jersey 07033.
Lunn
C A
CA
Senior
M M
MM
Zavodny
P J
PJ
Narula
S K
SK
D000595:Amino Acid Sequence; D000818:Animals; D004252:DNA Mutational Analysis; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics / Q000378:metabolism*; D008670:Metals / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000187:drug effects; D017471:Receptors, Interferon / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013045:Species Specificity; D013329:Structure-Activity Relationship; D000096743:Interferon gamma Receptor
D007371:Interferon-gamma; D008670:Metals; D017471:Receptors, Interferon; D011993:Recombinant Fusion Proteins; D000096743:Interferon gamma Receptor