Objective   To study the coexpression of protein folding modulators

including chaperones (DnaK

DnaJ

and GroEL-GroES) and disulfide isomerase Dsb molecules (DsbA and DsbC) on the bioactivity of eukaryotic expressed urokinase (UK).    Methods   The gene sequences of DnaK

DnaJ

GroEL-GroES

DsbA and DsbC were isolated from the chromosome of

E.coli

by PCR. The obtained fragments mentioned above were cloned into the plasmid pBAD-1 under the control of araB promoter and then the plasmids were transformed into

E.coli

BW25113 and HB101 together with a compatible vector pQE-UK. The amount of expressed UK was measured by Bradford method and its activity was analyzed by fibrin plate method for its fibrinolysis.     Results    The activity of

expressed UK was increased by co-expressing with DnaK

GroEL-GroES

DsbA

and DsbC in BW25113. Among them

the highest activity was achieved by co-expressing with GroEL-GroES.    Conclusion   Co-expressing of chaperones or disulfide isomerase can improve the bioactivity of UK expressed in

E. coli

.