Resolution and biological properties of three N-terminal analogues of recombinant human interleukin-1 beta.

Recombinant human interleukin-1 beta (rhuIL-1 beta) was purified to apparent homogeneity using standard procedures. The protein was characterized by N-terminal sequence analysis and found to consist of three forms: Met (20%), Ala (75%), and des-Ala (5%). Utilizing TSK SP 5PW HPLC, each form was resolved and analyzed by 2-D acrylamide gel electrophoresis. The analogues were identical in molecular mass (17,500 d) but differed in pI (Met, pI = 6.7; Ala, pI = 6.8; des-Ala, pI = 6.8). Bioactivity measurements, using the C3H/HeJ thymocyte proliferation assay, showed that native Ala rhuIL-1 beta was 300-400% more active than des-Ala rhuIL-1 beta, and was 400-600% more active than Met rhuIL-1 beta protein.