Im9 is the immunity protein made by E. coli at the same time as Colicin E9 to protect itself from the DNase activity of the colicin. Im9 binds with high affinity to colicin E9, and is only released upon entry of colicin E9 to a target E. coli cell. The structure shown is that of the Colicin E9 DNase domain bound to Im9[1]. When Im9 binds to colicin E9, 6 lysine residues become less accessible[2], and it is hypothesised that that the binding physically blocks one of the major dsDNA binding sites[3]. It is also hypothesised that the conformational dynamics of amino acids in the DNA binding domain change when Im9 binds, again preventing dsDNA binding[4].
Im9 is more flexible than ColE9, and when the complex is formed the backbone flexibility is then reduced[5].
References
- ↑ Angell CA, Ueno K. Materials science: Soft is strong. Nature. 2009 Nov 5;462(7269):45-6. PMID:19890319 doi:10.1038/462045a
- ↑ Scholten A, Visser NF, van den Heuvel RH, Heck AJ. Analysis of protein-protein interaction surfaces using a combination of efficient lysine acetylation and nanoLC-MALDI-MS/MS applied to the E9:Im9 bacteriotoxin--immunity protein complex. J Am Soc Mass Spectrom. 2006 Jul;17(7):983-94. Epub 2006 May 19. PMID:16713291 doi:10.1016/j.jasms.2006.03.005
- ↑ 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
- ↑ Scholten A, Visser NF, van den Heuvel RH, Heck AJ. Analysis of protein-protein interaction surfaces using a combination of efficient lysine acetylation and nanoLC-MALDI-MS/MS applied to the E9:Im9 bacteriotoxin--immunity protein complex. J Am Soc Mass Spectrom. 2006 Jul;17(7):983-94. Epub 2006 May 19. PMID:16713291 doi:10.1016/j.jasms.2006.03.005
- ↑ Baron R, Wong SE, de Oliveira CA, McCammon JA. E9-Im9 colicin DNase-immunity protein biomolecular association in water: a multiple-copy and accelerated molecular dynamics simulation study. J Phys Chem B. 2008 Dec 25;112(51):16802-14. PMID:19053689 doi:10.1021/jp8061543
