Bacterial expression and refolding of different fragments of human CD14

We have investigated bacterial expression of several fragments of CD14, a h uman cellular receptor for lipopolysaccharides (LPS). Despite binding of CD 14 to the LPS, a vital constituent of bacterial outer membrane, we have suc ceeded in producing full length recombinant hCD14 in E. coli. High level of production of CD14 resulted in deposits of aggregated CD14 in bacteria in form of inclusion bodies, which made production of this protein possible. W e have also produced N-terminal fragments consisting of 134 and 152 residue s, which comprise N-terminal domain with 2 and 3 leucine rich repeats, resp ectively and a fragment that contains only leucine rich repeats. Production of the N-terminal domain consisting of 69 residues could not be detected, probably due to the degradation of the produced protein within the bacteria . Full length CD14 and a fragment of 152 residues from inclusion bodies wer e refolded, while the 134 residues fragment and the one with 10 leucine-ric h repeats could not be refolded. Those results confirm that the minimal fol ding unit of CD14 must include N-terminal domain and at least 3 leucine ric h repeats.