The Thioredoxin
Reductase-deficient E.coli Mutant
Enhances Expression into Solution of Recombinant Proteins Containing Cys
Residues
TONG Qin,YANG Yun-Gui,ZHANG Hui-Tang,CHEN Yan,YANG
Sheng-Li,GONG Yi*
( Shanghai Research Center of Biotechnology, Chinese Academy of Sciences ,
Shang hai 200233, China )
Abstract A 3D
artificial protein, a salmon calcitonin hexa-polymer, a salmon calcitonin
octo-polymer and a human prourokinase, was expressed in the cytoplasma of E.coli
GJ980(trxB－) mutant. These recombinant proteins
containedcysteine residues of different length ranging from 12-22 residues. The
mutation was mapped to the gene for thioredoxin reductase(trxB) and was found
to eliminate the activity of this enzyme, which was thought to contribute to
the sulfhydryl reducing potential of the cytoplasm. Recombinant salmon
calcitonin hexapolymer, salmon calcitonin octo-polymer and human prourokinase
had more soluble form in cytoplasm of GJ980 mutants than in wild-type strain,
while 3D-protein, which has nocysteine residue, still remain in insoluble form.
Results indicate the GJ980(trxB－) strain allowed the formation
of disulphide bonds in the cell cytoplasm which is believed to encourage
correct folding and soluble expression of the recombinant proteins.
Key words expression system； soluble expression； thioredoxin reductase B
*Corresponding author：Tel,86-21-64700892-371；Fax,86-21-64700244；e-mail,[email protected]