GSK III is purified from Ecoli and it has a major contaminant Ecoli protein called GroE chaperone, which will run on a gel at approximately 90 kDa. This contaminant is not removed during purification because it stabilizes the protein. The GroE chaperone contamination does not affect GSK III activity. However, if you are in need of a homogenous GSK III protein NEB can supply you with a lot of GSK III in which the GroE chaperone has been removed. In order to purchase this special lot, please contact email@example.com.