I tried to express His-tagged IL-4, IL-13 and GM-CSF in E.coli. These proteins mainly accumulated as IB. During purification (after IB-purification and denaturation) proteins fragmented between His-tag and target protein.
Does anyone have any suggestions?
In addition, we are looking for a method for soluble expression of these proteins (optimize strain, vector, media, and induction conditions). IB-purification also seems to be inefficient (e.g endotoxin depletion). Does anyone have an optimize strategy for purification of IB, especially IB of cytokines and purification of renaturated cytokines preventing proteolysis?
Thanks for your efforts,