hGH purification from Trx-hGH expressed in <i>E. coli</i>.

<p>(A) Flowchart of the purification. (B) Trx-hGH was purified from <i>E. coli</i> with a combination of IMAC and gel filtration chromatography. M, molecular weight marker; lane 1, total cell protein before IPTG induction as a negative control; lane 2, total cell protein treated with IPTG; lane 3, soluble fraction after cell sonication; lane 4, Trx-hGH fusion protein purified using IMAC (37.4 kDa); lane 5, Trx tag cleavage with TEV protease: Trx (15.4 kDa) and hGH (22 kDa); lane 6, final purified hGH (22 kDa). Lane 5 shows that the Trx tag was almost completely cleaved. (C) Gel filtration chromatogram of PDIb′a′-hGH after second IMAC. hGH and oligomers were separated by their sizes. (D) Purity of final product hGH was evaluated by silver staining. M, molecular weight marker; hGH: final product in non-reducing conditions.