High-level production of recombinant human parathyroid hormone 1-34

Expression of the synthetic human parathyroid hormone 1-34 [hPTH(1-34)] gene by a gene fusion strategy was demonstrated. hPTH(1-34) was produced at the C terminus of the partner peptides involving amino acids 1 to 97, 1 to 117, or 1 to 139 of a modified Escherichia coli beta-galactosidase by linker peptides containing oligohistidine of different lengths. The fusion proteins in the inclusion bodies were rendered soluble with urea and subjected to site-specific cleavage with the secretory type yeast Kex2 protease. Optimal expression and enzymatic processing were achieved in the fusion protein beta G-117S4HPT, constructed from amino acids 1 to 117 of beta-galactosidase and the linker of HHHHPGGSVKKR. The fusion protein accumulated more than 20% of the E. coli total protein. The hPTH(1-34) was purified up to 99.5% with a good yield of 0.5 g/liter of culture. The purified product was identified as intact hPTH(1-34) by amino acid analysis and N-terminal sequencing.