Tol-Pal system, TolA (IPR014161)

Short name: Tol-Pal_TolA

Overlapping homologous superfamilies


Family relationships



Tol proteins are involved in the translocation of group A colicins. Colicins are bacterial protein toxins, which are active against Escherichia coli and other related species. TolA is anchored to the cytoplasmic membrane by a single membrane spanning segment near the N terminus, leaving most of the protein exposed to the periplasm [PMID: 12423782].

TolA couples the inner membrane complex of itself with TolQ and TolR to the outer membrane complex of TolB and OprL (also called Pal). Most of the length of the protein consists of low-complexity sequence that may differ in both length and composition from one species to another, complicating efforts to discriminate TolA (the most divergent gene in the tol-pal system) from paralogs such as TonB. Selection of members of the seed alignment and criteria for setting scoring cut-offs are based largely on conserved operon structure. The Tol-Pal complex is required for maintaining outer membrane integrity, and is also involved in transport (uptake) of colicins and filamentous DNA, and implicated in pathogenesis. Transport is energized by the proton motive force. TolA is an inner membrane protein that interacts with periplasmic TolB and with outer membrane porins OmpC, PhoE and LamB.

GO terms

Biological Process

GO:0043213 bacteriocin transport

Molecular Function

GO:0005215 transporter activity

Cellular Component

GO:0016021 integral component of membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.