View source for Colicin E4

Colicin E4 is a type of [[Colicin]], a bacteriocin made by ''E. coli'' which acts against other nearby ''E. coli'' to kill them with its [[16s rRNase activity]]; it digests the 16s ribosomal subunit, ultimately leading to the death of the cell. 

==Synthesis and release==

The colicin E4 operon is encoded on a plasmid in ''E. coli'', alongside a regulatory protein, and its [[Colicin Immunity Protein]], [[Im4]].

==Mechanism of uptake==

Colicin E4 binds first to the vitamin B12 [[BtuB]] outer membrane receptor on the target cell, via its receptor binding domain. Binding to this receptor triggers the immunity protein to release from the cytotoxic domain, so that when the colicin crosses the membrane it can kill the cell. Once bound to the BtuB receptor, ColE4 uses [[OmpF]] and the TolQRAB complex to cross the membrane, using a mechanism as yet unidentified.

==Killing Activities==

ColE4 kills the target cell with its [[16s rRNase activity]] where it enzymatically degrades its 16s rRNA subunit, and inhibits protein synthesis in the cell. This ultimately leads to the death of the cell.