The invention discloses the cloning, expression and uses of a chimeric fusion protein with superior chaperone and folding activities compared to the wild type chaperones. This invention relates to a chimeric fusion protein encoded by a recombinant DNA molecule containing nucleotide sequences coding for a polypeptide binding segment of a non-human chaperone protein and nucleotide sequences coding for an FK506 binding protein (FKBP) or an FK506-binding-protein-like domain (FKBP-like domain). In particular, this invention relates to a chimeric fusion protein encoded by a recombinant DNA molecule containing nucleotide sequences coding for a polypeptide binding segment of a non-human chaperone protein and nucleotide sequences coding for a human FKBP type peptidyl-prolyl-cis/trans isomerase (PPIase), methods of producing these chimeric fusion proteins and their uses as folding helpers in the production of other proteins and in the process of the production of vaccines or pharmaceuticals, and as folding helpers for performing immunoassays.