TolB

TolB has been shown to be essential for the function of the Tol system in Escherichia coli by generating an allosteric signal based on a conformational switch in the β-propeller region.

StructureStructure

TolB is a 44-kDa periplasmic protein associated with the outer membrane. 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) . 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.

FunctionFunction

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.

Related Tol entriesRelated Tol entries

• Tol
• TolQ
• TolR
• TolA
• Pal
• YbgF
• YbgC