Tol

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[[Tol-Colicin Complex]]
[[Tol-Colicin Complex]]
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[[Image:Tol Operon.jpg|600px|right|thumb| The Tol Operon]]
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[[Image:TOLn.jpg|600px|right|thumb| The Tol Operon]]
==Structure==
==Structure==

Revision as of 18:03, 7 February 2011

The Tol system, also known as Tol-Pal, is a multiprotein complex found in the cell envelope of many gram-negative bacteria. It contains 7 proteins (TolQ, TolR, TolA, TolB, Pal, YbgF, YbgC), whose respective genes are organized into two operons.

Tol-Colicin Complex

Image:TOLn.jpg
The Tol Operon

Contents

Structure

List of Tol proteinswith their properties
Protein Length (aa)[1] Accession Number[2]
TolQ 230 EFE63246
TolR 142 ZP_06661434
TolA 421 AAA24683
TolB 430 AAA24684
Pal 173 AP_001379
YbgF 116 YP_001729729
YbgC 134 NP_417224


Function

As of yet, the cellular role of the Tol proteins 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.[3]

Interaction of Tol proteins

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.[4]

Regulation

It has been shown that the regulation of Tol genes is linked to the cell envelope stability. [5] In studies with E. coli, the tol-pal genes have been induced by RcsC in response to cell envelope stress. [6] RcsC is a transmembrane sensor kinase, and along with the cytoplasmic response regulator RcsB, makes up the RcsBC regulatory system. [7] RcsBC is involved in the regulation of cps genes which code for the biosynthsis machinery of a major component for the capsula, cholanic acid.

References

  1. ↑ http://ecoliwiki.net/colipedia/index.php/Welcome_to_EcoliWiki
  2. ↑ http://www.ncbi.nlm.nih.gov/protein
  3. ↑ Dennis JJ, Lafontaine ER, Sokol PA. Identification and characterization of the tolQRA genes of Pseudomonas aeruginosa. J Bacteriol. 1996 Dec;178(24):7059-68. PMID:8955385
  4. ↑ Guihard G, Boulanger P, Benedetti H, Lloubes R, Besnard M, Letellier L. Colicin A and the Tol proteins involved in its translocation are preferentially located in the contact sites between the inner and outer membranes of Escherichia coli cells. J Biol Chem. 1994 Feb 25;269(8):5874-80. PMID:8119930
  5. ↑ Cascales E, Buchanan SK, Duche D, Kleanthous C, Lloubes R, Postle K, Riley M, Slatin S, Cavard D. Colicin biology. Microbiol Mol Biol Rev. 2007 Mar;71(1):158-229. PMID:17347522 doi:10.1128/MMBR.00036-06
  6. ↑ Clavel T, Lazzaroni JC, Vianney A, Portalier R. Expression of the tolQRA genes of Escherichia coli K-12 is controlled by the RcsC sensor protein involved in capsule synthesis. Mol Microbiol. 1996 Jan;19(1):19-25. PMID:8821933
  7. ↑ Majdalani N, Heck M, Stout V, Gottesman S. Role of RcsF in signaling to the Rcs phosphorelay pathway in Escherichia coli. J Bacteriol. 2005 Oct;187(19):6770-8. PMID:16166540 doi:10.1128/JB.187.19.6770-6778.2005

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Laura McCauley, Michal Harel

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