Colicin E7
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 releaseSynthesis and release
After synthesis inside the E. coli cell, the colicin binds its 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 uptakeMechanism of uptake
Killing ActivitiesKilling Activities
Colicin E7 has an endonuclease domain that degrades the DNA of the targeted cell, containing an H-N-H motif. This structure shows this domain bound to a DNA octamer [1].
The endonuclease domain is likely to use Zn2+[2] in the DNA cleavage, although other literature does not support this[3]. For cleavage of single stranded DNA or RNA ColE7 can either use Ni2+ or Co2+[4][5]. The bound ion binds to the second histadine residue in the HNH motif and stabilises the reaction.
ReferencesReferences
- ↑ Hsia KC, Chak KF, Liang PH, Cheng YS, Ku WY, Yuan HS. DNA binding and degradation by the HNH protein ColE7. Structure. 2004 Feb;12(2):205-14. PMID:14962381 doi:10.1016/j.str.2004.01.004
- ↑ Ku WY, Liu YW, Hsu YC, Liao CC, Liang PH, Yuan HS, Chak KF. The zinc ion in the HNH motif of the endonuclease domain of colicin E7 is not required for DNA binding but is essential for DNA hydrolysis. Nucleic Acids Res. 2002 Apr 1;30(7):1670-8. PMID:11917029
- ↑ Mate MJ, Kleanthous C. Structure-based analysis of the metal-dependent mechanism of H-N-H endonucleases. J Biol Chem. 2004 Aug 13;279(33):34763-9. Epub 2004 Jun 8. PMID:15190054 doi:10.1074/jbc.M403719200
- ↑ Keeble AH, Hemmings AM, James R, Moore GR, Kleanthous C. Multistep binding of transition metals to the H-N-H endonuclease toxin colicin E9. Biochemistry. 2002 Aug 13;41(32):10234-44. PMID:12162738
- ↑ Pommer AJ, Cal S, Keeble AH, Walker D, Evans SJ, Kuhlmann UC, Cooper A, Connolly BA, Hemmings AM, Moore GR, James R, Kleanthous C. Mechanism and cleavage specificity of the H-N-H endonuclease colicin E9. J Mol Biol. 2001 Dec 7;314(4):735-49. PMID:11733993 doi:10.1006/jmbi.2001.5189