Conversion of the biological specificity of murine to human leukemia inhibitory factor by replacing 6 amino acid residues.

Abstract

Mouse and human leukemia inhibitory factor (mLIF and hLIF) have approximately 80% amino acid identity, but mLIF cannot bind to the hLIF receptor (hLIF-R), while hLIF binds to the alpha-chain of the mLIF receptor (mLIF-R) with a much higher affinity than does mLIF. We have previously shown that the same regions confer both these properties of hLIF and map to an area within the predicted third alpha-helix and two of the loops of hLIF (Owczarek, C. M., Layton, M. J., Metcalf, D., Lock, P., Wilson, T. A., Gough, N. M., and Nicola, N. A. (1993) EMBO J. 12, 3487-3495). The present studies, using interspecies chimeras of mLIF and hLIF, have defined 6 residues (Asp57, Ser107, His112, Ser113, Val155, and Lys158) that contribute most of the binding energy involved in the interaction of hLIF and the hLIF-R alpha-chain, and form a surface at one end of the predicted four alpha-helical bundle of the hLIF molecule. Mouse LIF is unable to bind to the hLIF-R alpha-chain or activate the cellular hLIF-R, but when these 6 residues were substituted onto an mLIF framework, they were able to reconstitute both the binding and biological activities specific to hLIF.