Production of the beta-subunit of human chorionic gonadotropin in Escherichia coli and its export mediated by the heat-labile enterotoxin chain-B signal sequence.

The PCR-amplified beta-subunit of the human chorionic gonadotropin structural gene (betahCG) was cloned under the control of the tac promoter and the heat-labile enterotoxin chain B (LTB) signal sequence (LTBss). BetahCG was successfully produced, processed and exported to the periplasmic space in Escherichia coli. Expression of betahCG was confirmed by immunoblot analysis using an anti-betahCG polyclonal antibody. The processing of the protein was very efficient, as only the processed band could be detected at all time points during the course of induction. Expression was evident soon after the addition of the lactose analogue, IPTG. These results demonstrate that E. coli cells can synthesize, process and export betahCG using the LTBss.