Using BIACORE as Pots and Pans
We produced an extracellular domain of a receptor using the E. coli expression system. Though produced in substantial amounts, it did not dissolve at all because all of it had gone into inclusion bodies. It did not exhibit any activity, either, even after the pellet was solubilized with urea. Judging from the amino acid sequences deduced from cDNA, this protein has 10 cysteine residues and seems to have complicated disulphide bridges. We were puzzled whether we would be able to make an active form of the protein with E. coli. Or are sugar chains essential for its activity and which are lacking in the E. coli expression system? It would be easy to give up, because it isbe a long road to optimize the refolding conditions.