Tol

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Contents 1 Structure 2 Function 3 Interaction of Tol proteins 4 Interaction of Tol with Colicins 5 References

Structure

The Tol system, also known as Tol-Pal, is a multi-protein 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 as seen in the diagram.

Function

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.^[4]

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.^[5]

Interaction of Tol with Colicins

A yeast two-hybrid screen was carried out in order to determine the interactions between colicins and the Tol-Pal system during the import of colicin.^[6] In studies with E. coli, the tol-pal genes have been induced by RcsC in response to cell envelope stress. ^[7] RcsC is a transmembrane sensor kinase, and along with the cytoplasmic response regulator RcsB, makes up the RcsBC regulatory system. ^[8] 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. ↑ Witty M, Sanz C, Shah A, Grossmann JG, Mizuguchi K, Perham RN, Luisi B. Structure of the periplasmic domain of Pseudomonas aeruginosa TolA: evidence for an evolutionary relationship with the TonB transporter protein. EMBO J. 2002 Aug 15;21(16):4207-18. PMID:12169623
2. ↑ http://ecoliwiki.net/colipedia/index.php/tolA:Expression
3. ↑ http://ecoliwiki.net/colipedia/index.php/tolB:Expression
4. ↑ 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
5. ↑ 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
6. ↑ PMID: 11994151<ref></ref> The screen showed that TolB dimerizes, and its amino terminal domain (D1) interacts with the periplasmic, C-terminal domain of TolA (TolAIII), whilst the central domain of TolA (TolAII) interacts with YbgF. It is the interaction between TolAIII and D1 that forms a "trans-envelope complex" which brings the inner and outer membranes closer together allowing for the uptake of colicin A. The structure shows the interaction between TolB and the translocation domain of Colicin E9.

   spinqualitylabelsall models PDB ID 2ivz Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image
   2ivz, resolution 2.00Å ()
   Ligands:
   Related:	1bxi, 1c5k, 1crz, 1emv, 1fr2, 1fsj, 1v13, 1v14, 1v15
   Structural annotation: Resources: CATH : 2Ivza01, 2Ivza02, 2Ivzb02, 2Ivzb01, 2Ivzc01, 2Ivzc02, 2Ivzd01, 2Ivzd02 InterPro : Ipr011659, Ipr011042, Ipr014167, Ipr007195, Ipr011044, Ipr003058, Ipr003615, Ipr002711 Pfam : PF07676, PF04052 UniProt : P0A855, P09883
   Functional annotation: Cellular component: periplasmic space extrachromosomal circular DNA Biological process: protein import transport bacteriocin transport protein transport pathogenesis cytolysis defense response to bacterium Molecular function: protein binding nucleic acid binding hydrolase activity endonuclease activity nuclease activity receptor binding zinc ion binding metal ion binding
   Evolutionary conservation: Toggle Conservation Colors: Rows = identical sequences: Further Information: Caveats, Explanation, Complete Results at ConSurfDB
   Resources:	FirstGlance, OCA, RCSB, PDBsum
   Coordinates:	save as pdb, mmCIF, xml

   
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   Regulation

   It has been shown that the regulation of Tol genes is linked to the cell envelope stability. <ref>PMID: 17347522</li> <li id="cite_note-6">[[#cite_ref-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:[http://www.ncbi.nlm.nih.gov/pubmed/8821933 8821933] </li>

   <li id="cite_note-7">[[#cite_ref-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:[http://www.ncbi.nlm.nih.gov/pubmed/16166540 16166540] doi:[http://dx.doi.org/10.1128/JB.187.19.6770-6778.2005 10.1128/JB.187.19.6770-6778.2005]</li></ol></ref>