Role of unique consecutive glutamine repeats in active murine interleukin-2 molecule

Murine interleukin-2 (MIL-2) cDNA deleted of 11 repeats of a CAG sequence, and that encoded from 33Met to 149Gln were inserted into an expression vector carrying an Escherichia coli tryptophan promoter and were expressed in E. coli, respectively. Recombinant MIL-2 deleted of 11 glutamine repeats (MIL-2(-Gln] supported the growth of murine CTLL-2 cells but recombinant MIL-2 initiated from 34Asp (34Asp-MIL-2) did not. The growth of human T-cell blasts was not supported by MIL-2(-Gln) or 34Asp-MIL-2. MIL-2(-Gln) had identical biological and immunological activities with intact MIL-2, but 34Asp-MIL-2 did not. These results suggest that the consecutive glutamine repeats do not play a role in the biological and immunological activities of MIL-2, but that the peptide sequence around them does, and the species hierarchy that MIL-2 does not act on human lymphocyte is not due to the presence of glutamine repeats in MIL-2.