A fast and simple method to eliminate Cpn60 from functional recombinant proteins produced by E. coli Arctic Express

•Recombinant proteins produced in Arctic Express E. coli are contaminated by Cpn60.•A simple wash with subdenaturing urea concentration releases Cpn60.•Hydrophobic interactions are involved between Cpn60 and recombinant proteins.•After urea wash, an endoglucanase is fully active.•The protocol was successfully tested on a viral protein.

A frequent problem of recombinant protein production is their insolubility. To address this issue, engineered Escherichiacoli strains like Arctic Express that produce an exogenous chaperone facilitating protein folding, have been designed. A drawback is the frequent contamination of the protein by chaperones. A simple method, using urea at a sub-denaturing concentration, allows unbinding of Cpn60 from expressed protein. This method was successfully used to purify 2 proteins, an enzyme and a viral protein. The enzyme was fully active. The nature of interaction forces between enzyme and Cpn60 was investigated. The method is likely applicable to purify other proteins.