The Influence of Amino Acid Substitutions on the Function of Interleukin-2

The effects of some residues in IL-2 on its activity have been studied by site-directed mutagenesis. After changing 39 Met or 43 Lys to Pro, neither the CD spectra (s) nor the biological activities of these mutants were changed, implying that the 39 Met and 43 Lys were not involved in the reported alpha-helical structure. However after changing 52 Glu, 53 Leu or 54 Lys to Pro respectively the CD spectra were markedly changed and the activities were decreased significantly, showing that these three amino acids in IL-2 were integrated in the alpha-helix structure and very important for their biological functions. The significance of the above results was discussed.