Tol: Difference between revisions

As of yet, the cellular role of the Tol protein is unclear.  However, the system components are thought to be involved in the maintenance of the outer membrane as mutations of Tol proteins result in cells which leak the contents of the periplasm, as well as a hypersensitivity to some detergents, antibiotics and other agents.<ref>PMID: 8955385</ref>.  It is also thought to play a role in anchoring the outer membrane to the peptidoglycan layer through the interactions that occur between TolB, Pal, Lpp and OmpA<ref name='Bouveret'>PMID 7744736</ref>, as well as the regulation of porin activity due to the interactions seen between TolB and TolA<ref>PMID: 9393690</ref>.  

It was first suggested in 1994 that the Tol proteins interact to form a multiprotein complex of precise stoichiometry by Guihard et al, who showed that the level of Tol proteins at certain sites in the cell increases at a similar ratio with respect to one another when purified [[Colicin A]] is added to the whole cell.<ref>PMID: 8119930</ref>

* TolB has the ability to dimerize

<structure load='2ivz' size='300' align='right' caption='Interaction of TolB and Colicin E9' (PDB entry [[2ivz]]  |  SCENE= Tol/Tolbcol/1 />

The structure shows the interaction between [[TolB]] and the <scene name='Tol/Tolbcolclose/1'>translocation domain</scene> of [[Colicin E9]].

==Regulation==

It has been shown that the regulation of Tol genes is linked to the cell envelope stability.<ref>PMID: 17347522</ref>  In studies with E. coli, the ''tol-pal'' genes have been induced by RcsC in response to cell envelope stress.<ref>PMID: 8821933</ref>  RcsC is a transmembrane sensor kinase, and along with the cytoplasmic response regulator RcsB, makes up the RcsBC regulatory system.<ref>PMID: 16166540</ref>  RcsBC is involved in the regulation of ''cps'' genes which code for the biosynthsis machinery of a major component for the capsula, cholanic acid.