Partial purification and biological activity of the product of chemically synthesized human growth hormone gene expression in Escherichia coli

Synthesis and chromatographic purification of recombinant human pituitary hormones

Recombinant DNA-derived proteins and, in particular, human pituitary hormones, are increasingly used for research, diagnostic and therapeutic purposes. This trend has demanded new synthetic approaches and improved purification techniques. The type and sequence of the purification steps have to be selected in accordance with the cloning and protein expression strategy, the host organism and cellular localization of the protein of interest, with a view to producing the desired product at a required purity, biological activity and acceptable cost. This review article describes and analyzes the main synthetic and purification strategies that have been used for the production of recombinant human growth hormone, prolactin, thyrotropin, luteinizing hormone and follicle-stimulating hormone, giving special consideration to the few published downstream processes utilized by the biotechnology industry. Practically all types of prokaryotic and eukaryotic organisms utilized for this purpose are also reviewed.

Efficient expression, processing and secretion of a biologically active mammalian protein by Vibrio cholerae

The use of Vibrio cholerae as a secretory expression system for the expression of a mammalian protein, namely human growth hormone, under the control of the heat labile enterotoxin chain B signal sequence is reported. The protein is efficiently expressed and processed. The mature protein is exported to the periplasm after which it is secreted to the extracellular milieu. The expressed and secreted hGH actively binds to its receptor as established by its receptor binding activity. The biological activity of the protein is demonstrated in vitro in a Nb2 proliferation assay.

Efficient processing and export of human growth hormone by heat labile enterotoxin chain B signal sequence

The heat-labile enterotoxin chain B (LTB) signal sequence was used for the processing and export of human growth hormone (hGH). The protein was completely processed and exported across the cell membrane to accumulate in the periplasmic space in Escherichia coli. The human growth hormone cDNA was cloned as a PCR amplified fragment under the control of tac promoter and translationally fused to the LTB signal sequence. The rate of processing of hGH under the control of the LTB signal sequence was equal to or more than the rate of induction of expression, indicating efficient processing. The receptor binding activity of the processed periplasmic protein was established in a radio receptor assay.

Construction of an excretion vector and extracellular production of human growth hormone from Escherichia coli

A new excretion vector, pEAP8, was constructed to develop an excretion system for Escherichia coli. This plasmid, derived from pEAP37, carried the weakly activated kil gene of plasmid pMB9 [Kobayashi et al., J. Bacteriol. 166 (1986) 728-732] and the penicillinase promoter and signal region of an alkalophilic Bacillus sp. to excrete foreign gene products. A gene for human growth hormone (hGH) was joined to this signal sequence through the HindIII site. The recombinant plasmid p8hGH1 thus constructed, was introduced into E. coli. The hybrid protein which was produced in E. coli carrying p8hGH1 was processed during transport through the inner membrane, with the mature hGH being excreted into the medium through the outer membrane which was made permeable by the action of the kil gene. The N-terminal amino acid sequence and the biological activity of the extracellular hGH were consistent with those of the authentic hGH.