The trans-envelope Tol-Pal complex is part of the cell division machinery and required for proper outer-membrane invagination during cell constriction in E. coli

Mol Microbiol. 2007 Feb;63(4):1008-25. doi: 10.1111/j.1365-2958.2006.05571.x.


Fission of bacterial cells involves the co-ordinated invagination of the envelope layers. Invagination of the cytoplasmic membrane (IM) and peptidoglycan (PG) layer is likely driven by the septal ring organelle. Invagination of the outer membrane (OM) in Gram-negative species is thought to occur passively via its tethering to the underlying PG layer with generally distributed PG-binding OM (lipo)proteins. The Tol-Pal system is energized by proton motive force and is well conserved in Gram-negative bacteria. It consists of five proteins that can connect the OM to both the PG and IM layers via protein-PG and protein-protein interactions. Although the system is needed to maintain full OM integrity, and for class A colicins and filamentous phages to enter cells, its precise role has remained unclear. We show that all five components accumulate at constriction sites in Escherichia coli and that mutants lacking an intact system suffer delayed OM invagination and contain large OM blebs at constriction sites and cell poles. We propose that Tol-Pal constitutes a dynamic subcomplex of the division apparatus in Gram-negative bacteria that consumes energy to establish transient trans-envelope connections at/near the septal ring to draw the OM onto the invaginating PG and IM layers during constriction.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism*
  • Base Sequence
  • Cell Division
  • Cytoplasm / metabolism
  • Escherichia coli / cytology*
  • Escherichia coli / physiology*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Intracellular Membranes / metabolism
  • Lipoproteins / genetics
  • Lipoproteins / metabolism*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Molecular Sequence Data
  • Multiprotein Complexes
  • Mutation
  • Peptidoglycan / genetics
  • Peptidoglycan / metabolism*
  • Periplasmic Proteins / genetics
  • Periplasmic Proteins / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism


  • Bacterial Outer Membrane Proteins
  • Escherichia coli Proteins
  • ExcC protein, E coli
  • FtsN protein, E coli
  • Lipoproteins
  • Membrane Proteins
  • Multiprotein Complexes
  • Peptidoglycan
  • Periplasmic Proteins
  • Recombinant Fusion Proteins
  • tolA protein, E coli
  • tolB protein, E coli
  • Green Fluorescent Proteins