A unified model for BAM function that takes into account type Vc secretion and species differences in BAM composition

Jack C. Leo; Dirk Linke; Jack C. Leo; Dirk Linke

doi:10.3934/microbiol.2018.3.455

AIMS Microbiology

2018, Volume 4, Issue 3: 455-468. doi: 10.3934/microbiol.2018.3.455

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Commentary Topical Sections

A unified model for BAM function that takes into account type Vc secretion and species differences in BAM composition

Jack C. Leo ,
Dirk Linke ^,

Department of Biosciences, University of Oslo, Blindernveien 31, 0316 Oslo, Norway

Received: 11 May 2018 Accepted: 13 June 2018 Published: 22 June 2018

Transmembrane proteins in the outer membrane of Gram-negative bacteria are almost exclusively β-barrels. They are inserted into the outer membrane by a conserved and essential protein complex called the BAM (for β-barrel assembly machinery). In this commentary, we summarize current research into the mechanism of this protein complex and how it relates to type V secretion. Type V secretion systems are autotransporters that all contain a β-barrel transmembrane domain inserted by BAM. In type Vc systems, this domain is a homotrimer. We argue that none of the current models are sufficient to explain BAM function particularly regarding type Vc secretion. We also find that current models based on the well-studied model system Escherichia coli mostly ignore the pronounced differences in BAM composition between different bacterial species. We propose a more holistic view on how all OMPs, including autotransporters, are incorporated into the lipid bilayer.
- autotransport,
- protein secretion,
- Gram-negative bacteria,
- type V secretion,
- BAM,
- POTRA,
- TAM,
- outer membrane,
- transmembrane β-barrel,
- trimeric autotransporter adhesin
Citation: Jack C. Leo, Dirk Linke. A unified model for BAM function that takes into account type Vc secretion and species differences in BAM composition[J]. AIMS Microbiology, 2018, 4(3): 455-468. doi: 10.3934/microbiol.2018.3.455

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Abstract

Transmembrane proteins in the outer membrane of Gram-negative bacteria are almost exclusively β-barrels. They are inserted into the outer membrane by a conserved and essential protein complex called the BAM (for β-barrel assembly machinery). In this commentary, we summarize current research into the mechanism of this protein complex and how it relates to type V secretion. Type V secretion systems are autotransporters that all contain a β-barrel transmembrane domain inserted by BAM. In type Vc systems, this domain is a homotrimer. We argue that none of the current models are sufficient to explain BAM function particularly regarding type Vc secretion. We also find that current models based on the well-studied model system Escherichia coli mostly ignore the pronounced differences in BAM composition between different bacterial species. We propose a more holistic view on how all OMPs, including autotransporters, are incorporated into the lipid bilayer.

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