1988 Volume 104 Issue 5 Pages 837-840
Using the expression system for site-specific mutagenesis in Escherichia coli, we have made deletion mutants at the N-terminal or C-terminal region of human interleukin-1β (IL-1β) consisting of 153 amino acids. The truncated mutants showed that at least 147 amino acids (numbers 4-150) in IL-1β are necessary for the exertion of biological activity. When we changed the arginine at the 4th position (Arg4) in IL-1β to other specific amino acids, there was a marked difference in the relative extent of biological and receptor binding activities among the mutants. The order of the mutants was Arg4=Lys4>Gln4>Gly4=des-Arg4>Asp4. Our results demonstrate that the arginine residue at the 4th position in IL-1β is important, but not essential, for IL-1β to exhibit its biological and receptor binding activities, and the positive charge at this site plays a key role for IL-1β to exert the activities.
