Disclosed are a recombinant DNA molecule encoding a fusion protein comprising a SlpA chaperone and a target polypeptide wherein human FK506 binding proteins (FKBPs) are excluded as target polypeptides, a corresponding expression vector encoding said fusion protein as well as host cells transformed with said expression vector. Also disclosed are a method for producing the fusion protein, a recombinantly produced fusion protein comprising a SlpA chaperone and a target polypeptide. A further aspect of the invention is the use of the recombinantly produced fusion protein, and a reagent kit containing a recombinantly produced fusion protein comprising a SlpA chaperone and a target polypeptide.