Internal deletions of amino acids 29-42 of human interleukin-6 (IL-6) differentially affect bioactivity and folding

Abstract

Internal deletions of the human interleukin-6 (IL-6) cDNA have been generated in the region encoding residues 29 to 42. Mutant proteins were produced by in vitro transcription—translation or in Escherichia coli and tested for their biological activity using the hybridoma growth factor (HGF) assay or a transcriptional activation assay on human hepatoma cells. The folding of the mutants was also checked by immunoprecipitation with conformation-specific monoclonal antibodies. The results show that only residues 29 to 34 are crucial for IL-6 activity and that the first two amino acids are probably involved in the definition of the IL-6 active site.