Biologically Active Recombinant Human Progastrin6-80 Contains a Tightly Bound Calcium Ion

Abstract

Evidence is accumulating that gastrin precursors may act as growth factors for the colonic mucosa in vivo. The aims of this study were to prepare recombinant human progastrin6-80 and to investigate its structure and biological activities in vitro. Human progastrin6-80 was expressed in Escherichia coli as a glutathione S-transferase fusion protein. After thrombin cleavage progastrin6-80 was purified by reverse phase high pressure liquid chromatography and characterized by radio-immunoassay, amino acid sequencing, and mass spectrometry. Assays for metal ions by atomic emission spectroscopy revealed the presence of a single tightly bound calcium ion. Progastrin6-80 at concentrations in the pM t..