Document Type : Original Research Article



Most of proteins produced in Escherichia coli accumulate as insoluble inclusion bodies. Optimal secretion of the recombinant protein can be obtained by a desirable signal peptide .In this research, we used Bacillus. sp endoxylanase signal peptide in order to guide the human growth hormone (HGH) to the periplasmic space as an effective approach for production of an active and non-immunogenic form of rHGH without formyl methionine at the N-terminus. The signal sequence was fused to the growth hormone gene and cloned in pET 28a+ vector under the T7 promoter and transformed to Ecoli، Rosetta gami and BL21 (DE3) strains. The bacterial cells in log phase indused by 0.25 mM of IPTG. Osmotic shock used to releas periplasmic components followed by SDS-PAGE and eventually confirmed by western blot. The results showed a high portion of rHGH transferred to the periplasmic space that means xylA signal peptide successfully led to the protein to periplasm. Among the tested constructs, pET28a+xyla-rHGH in E. coli Rosetta gami had 12.49 % of rHGH band depending on Imag J software analysis. Presence of soluble form of rHGH in periplasmic space seems to be a good indication for expression of f-Met free rHGH.