Overproduction of Campylobacter Ferritin in Escherichia coli and Induction of Paracrystalline Inclusion by Ferrous Compound

Abstract

The ferritin gene (cft) of Campylobacter jejuni was overexpressed in cells of Escherichia coli using a T7 RNA polymerase expression system. Many round particles which were the same size as the ferritin particles purified from C. jejuni were observed in the lysate of the cft-overexpressed E. coli cells. Since most of them were devoid of a central electron dense core consisting of ferric irons, the Campylobacter ferritins overproduced in E. coli seemed to be apoferritin. When large amounts of ferrous iron (supplied as FeSO₄) were added to culture medium, the cft-overexpressed cells formed large inclusion bodies of paracrystalline arrays comprised of ferritin particles with central electron dense cores. The addition of ferric irons did not produce paracrystalline inclusion.