TolB: Difference between revisions

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==Structure==

TolB is a 44-kDa periplasmic protein partially associated with the outer membrane<ref name='Bouveret'>PMID: 7744736</ref>. It has two domains: an N-terminal α/β domain and a C-terminal six-bladed β-propeller (to which [[Pal]] and [[Colicin E9]] bind)<ref>PMID: 19696740</ref>. The β-propeller has a latching or ‘Velco’ strand which joins the first and last of the six blades, and is positioned in the domain-domain interface. When Pal binds to the C-terminus of TolB, the latching strand moves away from the interface and carries with it a proline residue. The movement of the latching strand opens up a canyon that would normally be buried between the N- and C-terminal domains of TolB. This canyon can now be used as a binding site for the N-terminal of TolB, which forms a helical half-turn and a β-sheet against the canyon.

TolB is a 44-kDa periplasmic protein partially associated with the outer membrane<ref name='Bouveret'>PMID: 7744736</ref>. It has two domains: an N-terminal α/β domain and a C-terminal six-bladed β-propeller (to which [[Pal]] and [[Colicin E9]] bind)<ref name='Bonsor'>PMID: 19696740</ref>. The β-propeller has a latching or ‘Velco’ strand which joins the first and last of the six blades, and is positioned in the domain-domain interface. When Pal binds to the C-terminus of TolB, the latching strand moves away from the interface and carries with it a proline residue. The movement of the latching strand opens up a canyon that would normally be buried between the N- and C-terminal domains of TolB. This canyon can now be used as a binding site for the N-terminal of TolB, which forms a helical half-turn and a β-sheet against the canyon.

==Function==

The distal N-terminal 12 residues of TolB has two conformational states which are governed by protein-protein interactions with the β -propeller and results in the binding of [[TolA]] in the inner membrane<ref>PMID: 19696740</ref>.

The distal N-terminal 12 residues of TolB has two conformational states which are governed by protein-protein interactions with the β -propeller and results in the binding of [[TolA]] in the inner membrane<ref name='Bonsor'>PMID: 19696740</ref>.

TolB has been shown to be essential for the function of the [[Tol]] system in ''Escherichia coli''<ref>PMID: 19696740</ref> by generating an allosteric signal based on a conformational switch in the β-propeller region. TolB has also been shown to interact with the porins of Escherichia coli, in particular OmpF, OmpC, PhoE and LamB, but not OmpA or any of their denatured counterparts. It has been proposed that the whole Tol complex plays a role in this association, although "tol" mutants do not prevent this assembly completely therefore the Tol system may be involved kinetically, not directly<ref>PMID: 9393690</ref>.

TolB has been shown to be essential for the function of the [[Tol]] system in ''Escherichia coli''<ref name='Bonsor'>PMID: 19696740</ref> by generating an allosteric signal based on a conformational switch in the β-propeller region. TolB has also been shown to interact with the porins of Escherichia coli, in particular OmpF, OmpC, PhoE and LamB, but not OmpA or any of their denatured counterparts. It has been proposed that the whole Tol complex plays a role in this association, although "tol" mutants do not prevent this assembly completely therefore the Tol system may be involved kinetically, not directly<ref>PMID: 9393690</ref>.

==The TolB-Pal Complex==

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 {{STRUCTURE_1c5k |  PDB=1c5k  |  SCENE= TolB/Tolb/1 }}
 ==Structure==
-TolB is a 44-kDa periplasmic protein partially associated with the outer membrane<ref name='Bouveret'>PMID: 7744736</ref>.  It has two domains: an N-terminal α/β domain and a C-terminal six-bladed β-propeller (to which [[Pal]] and [[Colicin E9]] bind)<ref>PMID: 19696740</ref>.  The β-propeller has a latching or ‘Velco’ strand which joins the first and last of the six blades, and is positioned in the domain-domain interface.  When Pal binds to the C-terminus of TolB, the latching strand moves away from the interface and carries with it a proline residue.  The movement of the latching strand opens up a canyon  that would normally be buried between the N- and C-terminal domains of TolB.  This canyon can now be used as a binding site for the N-terminal of TolB, which forms a helical half-turn and a β-sheet against the canyon.
+TolB is a 44-kDa periplasmic protein partially associated with the outer membrane<ref name='Bouveret'>PMID: 7744736</ref>.  It has two domains: an N-terminal α/β domain and a C-terminal six-bladed β-propeller (to which [[Pal]] and [[Colicin E9]] bind)<ref name='Bonsor'>PMID: 19696740</ref>.  The β-propeller has a latching or ‘Velco’ strand which joins the first and last of the six blades, and is positioned in the domain-domain interface.  When Pal binds to the C-terminus of TolB, the latching strand moves away from the interface and carries with it a proline residue.  The movement of the latching strand opens up a canyon  that would normally be buried between the N- and C-terminal domains of TolB.  This canyon can now be used as a binding site for the N-terminal of TolB, which forms a helical half-turn and a β-sheet against the canyon.
 ==Function==
-The distal N-terminal 12 residues of TolB has two conformational states which are governed by protein-protein interactions with the β -propeller and results in the binding of [[TolA]] in the inner membrane<ref>PMID: 19696740</ref>.
+The distal N-terminal 12 residues of TolB has two conformational states which are governed by protein-protein interactions with the β -propeller and results in the binding of [[TolA]] in the inner membrane<ref name='Bonsor'>PMID: 19696740</ref>.
-TolB has been shown to be essential for the function of the [[Tol]] system in ''Escherichia coli''<ref>PMID: 19696740</ref> by generating an allosteric signal based on a conformational switch in the β-propeller region.  TolB has also been shown to interact with the porins of Escherichia coli, in particular OmpF, OmpC, PhoE and LamB, but not OmpA or any of their denatured counterparts.  It has been proposed that the whole Tol complex plays a role in this association, although "tol" mutants do not prevent this assembly completely therefore the Tol system may be involved kinetically, not directly<ref>PMID: 9393690</ref>.
+TolB has been shown to be essential for the function of the [[Tol]] system in ''Escherichia coli''<ref name='Bonsor'>PMID: 19696740</ref> by generating an allosteric signal based on a conformational switch in the β-propeller region.  TolB has also been shown to interact with the porins of Escherichia coli, in particular OmpF, OmpC, PhoE and LamB, but not OmpA or any of their denatured counterparts.  It has been proposed that the whole Tol complex plays a role in this association, although "tol" mutants do not prevent this assembly completely therefore the Tol system may be involved kinetically, not directly<ref>PMID: 9393690</ref>.
 ==The TolB-Pal Complex==