Patent ID: 8685668

Claim:
A method of expressing in prokaryotic host cells a eukaryotic protein that requires formation of multiple interchain or intrachain disulfide bridges for its biological activity, said method comprising: a) transforming a prokaryotic host cell with an expression vector encoding a fusion protein which comprises an N-terminal segment encoding thioredoxin and a C-terminal segment encoding a eukaryotic protein that requires formation of at least two intrachain or interchain disulfide bridges for biological activity; and b) expressing said eukaryotic protein fused to said thioredoxin in biologically active form, wherein the host cell has been modified to express a disulfide isomerase DsbC in the cytoplasm of the cell, and wherein the DsbC has the amino acid sequence as set forth in SEQ ID NO: 3 which is modified so that its active site sequence between positions 98-101 has been changed to CGFC (SEQ ID NO: 45) or CTFC (SEQ ID NO: 46).