Preparation of biologically active recombinant human progastrin(1-80)

The bacterial expression of human progastrin(6-80) has been reported previously [Baldwin, G.S. et al. (2001) J. Biol. Chem. 276: 7791-7796]. The aims of the present study were to prepare full-length recombinant human progastrin(1-80) and to compare its biological activity with that of progastrin(6-80) in vitro, to determine whether or not the N-terminal five amino acids contributed to activity. A fusion protein of glutathione-S-transferase and human progastrin(1-80) was expressed in Escherichia coli, collected on glutathione-agarose beads, and cleaved with enterokinase. Progastrin(1-80) was purified by reversed-phase and anion exchange HPLC and characterized by radioimmunoassay, amino acid sequencing, and mass spectrometry. No differences were detected in the extent of stimulation by progastrin(1-80) and progastrin(6-80) in proliferation and migration assays with the mouse gastric cell line IMGE-5. We conclude that residues 1-5 of progastrin(1-80) are not essential for biological activity.