Reduction of biological activity of murine recombinant interleukin-1 beta by selective deamidation at asparagine-149.

A biologically active preparation of murine recombinant interleukin-1 beta (mIL-1 beta) from Escherichia coli cell lysates contained tow forms of mIL-1 beta with pI 8.7 and pI 8.1, respectively. Treatment with 0.1 M Tris, pH 8.5, at 37 degrees C for 35 h converted the pI 8.7 form to the pI 8.1 form by the selective deamidation of an asparagine residue (Asn149) in the mIL-1 beta molecule. Deamidated mIL-1 beta had 3- to 5-fold lower co-mitogenic activity and receptor affinity than the unmodified form.