STRUCTURE-ACTIVITY-RELATIONSHIPS IN HUMAN INTERLEUKIN-1-ALPHA - IDENTIFICATION OF KEY RESIDUES FOR EXPRESSION OF BIOLOGICAL-ACTIVITIES

To identify the sites important for the different biological activitie s of human interleukin-1-alpha (hIL-1-alpha), 56 single-amino acid-sub stituted mutants of hIL-1-alpha were produced in Escherichia coli usin g site-directed mutagenesis, and were examined for their biological ac tivities such as mouse lymphocyte activating factor activity (LAF acti vity), cytostatic activity against human melanoma cells A-375 (A375 ac tivity) and prostaglandin E2 (PGE2) inducing activity in human osteosa rcoma cells MG-63 (PEI activity). Two amino acid residues, Asp26 and A sp151, were found to be important for these activities. The replacemen t of Asp26 by Val caused a decrease in LAF and PEI activities by one o r two orders of magnitude and a slight decrease in A375 activity. The Tyr or Phe substitution for Asp151 caused decreases in LAF and A375 ac tivities by one or two orders of magnitude and complete loss of PEI ac tivity. The change from Asp151 to Lys or Arg resulted in marked decrea se in LAF activity and complete loss of A375 and PEI activities. Since Asp26 and Asp151 are close to each other in the three-dimensional str ucture, the region involving these amino acids seems to be important f or the biological activities of hIL-1-alpha.