Processing of DNase domain during translocation of colicin E7 across the membrane of Escherichia coli

Translocation of colicin across the membrane of sensitive cells has been st udied extensively. However, processing of the toxicity domain of colicin du ring translocation has been the subject of much controversy. To investigate the final translocation product of colicin across the membrane of Escheric hia coli, an endogenously expressed His-tagged Im7 protein was constructed to detect any translocation product containing the DNase domain traversed t he inner membrane into cytoplasm of the E. coli cells. As a result, a final processed DNase domain of ColE7 was identified in the intracellular space of the cells treated with Col-Im complex. In the presence of periplasmic ex tracts, in vitro processing of DNase domain of ColE7 was also observed. The se results suggest that the processing of ColE7 has occurred for translocat ion of the DNase-type colicin across the membrane and the process is probab ly taking place in the periplasmic space of the membrane. (C) 2001 Academic Press.