View source for Colicin E7

<StructureSection load='2axc' size='450' side='right' scene='Colicin_E7/Cole7t/1' caption=''>
Colicin E7 is a type of [[Colicin]], a bacteriocin made by ''E. coli'' which acts against other nearby ''E. coli'' to kill them with its [[DNase Activity]]; it digests the cell's genome in specific locations, ultimately leading to the death of the cell. 

==Synthesis and release==
After synthesis inside the ''E. coli'' cell, the colicin binds its [[Colicin Immunity Protein]], [[Im7]], to its nuclease domain, to prevent the host cell from being killed by its activity. This immunity protein is released only on binding to the outer membrane of the target cell.

==Mechanism of uptake==

The receptor binding domain of ColE7 binds to the [[BtuB]] vitamin B12 receptor on the outer membrane of the target cell. This causes the dissociation of the immunity protein from the cytotoxic domain of the colicin, allowing it to target the cell when it enters. Binding BtuB triggers the recruitment of [[OmpF]] and the TolQRAB complex, to bind to the translocation domain and translocate the colicin across the membrane. The mechanism by which this occurs has not yet been identified. This structure shows the translocation domain of ColE7.

==Killing Activities==


<scene name='Colicin_E7/Cole7cmono/1'>Colicin E7</scene> has an endonuclease domain that degrades the DNA of the targeted cell, containing an [[H-N-H motif]]. This structure shows <scene name='Colicin_E7/Cole7c/1'>this domain</scene> bound to a <scene name='Colicin_E7/Dnaoctomer/1'>DNA octamer</scene><ref> PMID: 14962381 </ref>.

The endonuclease domain is likely to use Zn<sup>2+</sup><ref> PMID: 11917029 </ref> in the DNA cleavage, although other literature does not support this<ref> PMID: 15190054 </ref>. For cleavage of single stranded DNA or RNA ColE7 can either use Ni<sup>2+</sup> or Co<sup>2+</sup><ref>PMID: 12162738</ref><ref>PMID: 11733993 </ref>. The bound ion binds to the second histadine residue in the HNH motif and stabilises the reaction.
</StructureSection>
==References==

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