Structure and function of bacterial outer membrane proteins: barrels in a nutshell

Mol Microbiol. 2000 Jul;37(2):239-53. doi: 10.1046/j.1365-2958.2000.01983.x.


The outer membrane protects Gram-negative bacteria against a harsh environment. At the same time, the embedded proteins fulfil a number of tasks that are crucial to the bacterial cell, such as solute and protein translocation, as well as signal transduction. Unlike membrane proteins from all other sources, integral outer membrane proteins do not consist of transmembrane alpha-helices, but instead fold into antiparallel beta-barrels. Over recent years, the atomic structures of several outer membrane proteins, belonging to six families, have been determined. They include the OmpA membrane domain, the OmpX protein, phospholipase A, general porins (OmpF, PhoE), substrate-specific porins (LamB, ScrY) and the TonB-dependent iron siderophore transporters FhuA and FepA. These crystallographic studies have yielded invaluable insight into and decisively advanced the understanding of the functions of these intriguing proteins. Our review is aimed at discussing their common principles and peculiarities as well as open questions associated with them.

Publication types

  • Review

MeSH terms

  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism
  • Biological Transport
  • Conserved Sequence
  • Escherichia coli Proteins*
  • Gram-Negative Bacteria / chemistry*
  • Gram-Negative Bacteria / metabolism
  • Hydrolases*
  • Membrane Proteins / chemistry
  • Membrane Proteins / metabolism
  • Models, Molecular
  • Phospholipases A / chemistry
  • Phospholipases A / metabolism
  • Porins / chemistry
  • Porins / metabolism
  • Protein Structure, Secondary
  • Signal Transduction


  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Escherichia coli Proteins
  • Membrane Proteins
  • Porins
  • tonB protein, Bacteria
  • OmpX protein, E coli
  • OMPA outer membrane proteins
  • Hydrolases
  • Phospholipases A