Patent ID: 8822650

Claim:
A method of producing an immunoglobulin constant region, comprising: (a) transforming an E. coli cell with a recombinant expression vector comprising (i) a nucleotide sequence encoding E. coli heat-stable enterotoxin II signal sequence and (ii) a nucleotide sequence encoding the immunoglobulin constant region without a variable region; (b) culturing a resulting E. coli transformant in a medium; and (c) isolating the immunoglobulin constant region expressed by the transformant, wherein the E. coli heat-stable enterotoxin II signal sequence is cleaved by a signal peptidase, and consists of the amino acid sequence of SEQ ID NO. 36, 37, 38, 39, 40, 41, 42, 43, 44, 45 or 46, wherein the immunoglobulin constant region is expressed in the cytoplasm in a water soluble form and is not secreted into the medium or the periplasmic space.