Expression, secretion and folding of human growth hormone in Escherichia coli. Purification and characterization

An efficient secretion vector containing a gene coding for an E. coli signal peptide fused to human growth hormone (hGH) was cloned into E. coli. The recombinant fusion protein was expressed and correctly processed hGH was secreted into the periplasmic space at a yield of 10-15 micrograms hGH/A600. Purification of hGH from the periplasmic fraction by anion exchange and size exclusion gave hGH of greater than 90% purity. Characterization by SDS-PAGE, amino terminal analysis, trypsin mapping, and circular dichroism demonstrated that the fusion protein was correctly processed to authentic hGH and that the E. coli periplasm provided an appropriate environment for proper folding of hGH and disulfide bond formation.