Tol: Difference between revisions

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[[Image:TOL.jpg|400px|right|thumb| The Tol System<ref name='Witty'> PMID: 12169623</ref> and Operon<ref>http://ecoliwiki.net/colipedia/index.php/tolA:Expression</ref><ref>http://ecoliwiki.net/colipedia/index.php/tolB:Expression</ref> ]]

==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<ref name="Cascales">PMID: 17347522</ref>.

===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.<ref>PMID: 8119930</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>.

Cross-linking experiments show that<ref>PMID: 10419942</ref>:

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Line 17:

==Function==

As of yet, the cellular role of the Tol protein is unclear. However, there are several proposals for the different functions it may carry out:

* the system components could 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>.

* the system components could 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 may 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>,

* it may 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>

* possible regulation of porin activity due to the interactions seen between TolB and TolA<ref>PMID: 9393690</ref>.

* possible regulation of porin activity due to the interactions seen between TolB and TolA<ref>PMID: 9393690</ref>

* the Tol-Pal system may have the ability to localise in the membrane to a site of cell constriction, taking part in invagination of the outer membrane during cell division<ref>PMID: 17233825</ref>

===Interaction of Tol with Colicins===

The Tol-Pal system is used by group A colicins in order to translocate across the outer membrane, targeting mainly the inner membrane component TolA as well as TolQ and TolR. The colicins set up a translocon, constituting of the outer membrane receptor, translocator proteins and one or more periplasmic translocator proteins. The colicins recruit the Tol proteins using a Tol binding antigen, or epitope, which is embedded in the IUTD (Intrinsically Unstructured [[Translocation domain]]) found on the N-terminal (T-) domain of the colicin<ref>PMID: 21060316</ref>.

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.<ref name="Walburger">PMID: 11994151</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 N-terminal of the group A colicins then interact with TolA and also sometimes TolB during translocation into the inner membrane.

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<ref name="Walburger">PMID: 11994151</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 N-terminal of the group A colicins then interact with TolA and also sometimes TolB during translocation into the inner membrane.

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

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 name="Cascales">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.

It has been shown that the regulation of Tol genes is linked to the cell envelope stability<ref name="Cascales">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.

== References==

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@@ Line 1: / Line 1: @@
 [[Image:TOL.jpg|400px|right|thumb| The Tol System<ref name='Witty'> PMID: 12169623</ref> and Operon<ref>http://ecoliwiki.net/colipedia/index.php/tolA:Expression</ref><ref>http://ecoliwiki.net/colipedia/index.php/tolB:Expression</ref> ]]
 ==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<ref name="Cascales">PMID: 17347522</ref>.
 ===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.<ref>PMID: 8119930</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>.
 Cross-linking experiments show that<ref>PMID: 10419942</ref>:
@@ Line 18: / Line 17: @@
 ==Function==
 As of yet, the cellular role of the Tol protein is unclear.  However, there are several proposals for the different functions it may carry out:
-* the system components could 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>.
+* the system components could 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 may 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>,
+* it may 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>
-* possible regulation of porin activity due to the interactions seen between TolB and TolA<ref>PMID: 9393690</ref>.
+* possible regulation of porin activity due to the interactions seen between TolB and TolA<ref>PMID: 9393690</ref>
 * the Tol-Pal system may have the ability to localise in the membrane to a site of cell constriction, taking part in invagination of the outer membrane during cell division<ref>PMID: 17233825</ref>
 ===Interaction of Tol with Colicins===
 <structure load='2ivz' size='300' align='right' caption='Interaction of TolB and Colicin E9' (PDB entry [[2ivz]]  |  SCENE= Tol/Tolbcol/1 />
 The Tol-Pal system is used by group A colicins in order to translocate across the outer membrane, targeting mainly the inner membrane component TolA as well as TolQ and TolR.  The colicins set up a translocon, constituting of the outer membrane receptor, translocator proteins and one or more periplasmic translocator proteins.  The colicins recruit the Tol proteins using a Tol binding antigen, or epitope, which is embedded in the IUTD (Intrinsically Unstructured [[Translocation domain]]) found on the N-terminal (T-) domain of the colicin<ref>PMID: 21060316</ref>.
-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.<ref name="Walburger">PMID: 11994151</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 N-terminal of the group A colicins then interact with TolA and also sometimes TolB during translocation into the inner membrane.
+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<ref name="Walburger">PMID: 11994151</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 N-terminal of the group A colicins then interact with TolA and also sometimes TolB during translocation into the inner membrane.
-The structure shows the interaction between [[TolB]] and the <scene name='Tol/Tolbcolclose/1'>translocation domain</scene> of [[Colicin E9]].
+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 name="Cascales">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.
+It has been shown that the regulation of Tol genes is linked to the cell envelope stability<ref name="Cascales">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.
 == References==
 <references/>