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Evolution of the Translocation and Assembly Module (TAM).

Heinz E, Selkrig J, Belousoff MJ, Lithgow T - Genome Biol Evol (2015)

Bottom Line: We report that TamA and a closely related protein TamL are confined almost exclusively to Proteobacteria and Bacteroidetes/Chlorobi respectively, whereas TamB is widely distributed across the majority of Gram-negative bacterial lineages.Several sequence characteristics were discovered to define the TamB protein family: A signal-anchor linkage to the inner membrane, beta-helical structure, conserved domain architecture and a C-terminal region that mimics outer membrane protein beta-strands.Taken together, the structural and phylogenetic analyses suggest that the TAM likely evolved from an original combination of BamA and TamB, with a later gene duplication event of BamA, giving rise to an additional Omp85 sequence that evolved to be TamA in Proteobacteria and TamL in Bacteroidetes/Chlorobi.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Monash University, Melbourne, Victoria, Australia.

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The BAM and the TAM in E. coli. The two Omp85 proteins BamA and TamA are membrane-embedded beta-barrels, with their POTRA domains extending into the periplasm. In E. coli, BamA interacts with four lipoprotein partners: BamB, BamC, BamD, and BamE to form the BAM complex. The TAM is formed from TamA in the outer membrane and the innermembrane anchored protein TamB. Sequence analysis suggests a relationship between the TamB protein family and the AsmA protein family. In E. coli, the inner membrane protein AsmA is not known to interact with any outer membrane protein partner.
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evv097-F1: The BAM and the TAM in E. coli. The two Omp85 proteins BamA and TamA are membrane-embedded beta-barrels, with their POTRA domains extending into the periplasm. In E. coli, BamA interacts with four lipoprotein partners: BamB, BamC, BamD, and BamE to form the BAM complex. The TAM is formed from TamA in the outer membrane and the innermembrane anchored protein TamB. Sequence analysis suggests a relationship between the TamB protein family and the AsmA protein family. In E. coli, the inner membrane protein AsmA is not known to interact with any outer membrane protein partner.

Mentions: Bacterial outer membrane proteins show a range of complexity in their domain arrangements, ranging from comparatively simple porins to large and complex molecules such as autotransporters, intimins, and invasins. The canonical structure for the membrane-embedded domain of these proteins is a beta-barrel, composed of antiparallel beta-strands. After synthesis in the cytoplasm, beta-barrel proteins reach the periplasm in an unfolded state, and are then folded and inserted into the outer membrane by the beta-barrel assembly machinery (BAM, fig. 1; Knowles et al. 2009; Hagan et al. 2011; Selkrig et al. 2013). The BAM complex in Escherichia coli consists of five subunits, BamA–E (fig. 1). BamA is essential (Genevrois et al. 2003; Voulhoux et al. 2003) and is found in all Gram-negative bacteria (Heinz and Lithgow 2014). As a member of the Omp85 protein family, BamA is itself a membrane-embedded beta-barrel protein (Noinaj et al. 2013) with several periplasmic polypeptide transport-associated (POTRA) domains (fig. 1). BamD, the other component essential in Proteobacteria, has also been identified in other groups of bacteria (Anwari et al. 2012; Webb et al. 2012), whereas other components of the BAM complex in E. coli, BamB, BamC, and BamE are outer membrane lipoproteins found only in subsets of the Proteobacteria (Anwari et al. 2012; Webb et al. 2012).Fig. 1.—


Evolution of the Translocation and Assembly Module (TAM).

Heinz E, Selkrig J, Belousoff MJ, Lithgow T - Genome Biol Evol (2015)

The BAM and the TAM in E. coli. The two Omp85 proteins BamA and TamA are membrane-embedded beta-barrels, with their POTRA domains extending into the periplasm. In E. coli, BamA interacts with four lipoprotein partners: BamB, BamC, BamD, and BamE to form the BAM complex. The TAM is formed from TamA in the outer membrane and the innermembrane anchored protein TamB. Sequence analysis suggests a relationship between the TamB protein family and the AsmA protein family. In E. coli, the inner membrane protein AsmA is not known to interact with any outer membrane protein partner.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4494059&req=5

evv097-F1: The BAM and the TAM in E. coli. The two Omp85 proteins BamA and TamA are membrane-embedded beta-barrels, with their POTRA domains extending into the periplasm. In E. coli, BamA interacts with four lipoprotein partners: BamB, BamC, BamD, and BamE to form the BAM complex. The TAM is formed from TamA in the outer membrane and the innermembrane anchored protein TamB. Sequence analysis suggests a relationship between the TamB protein family and the AsmA protein family. In E. coli, the inner membrane protein AsmA is not known to interact with any outer membrane protein partner.
Mentions: Bacterial outer membrane proteins show a range of complexity in their domain arrangements, ranging from comparatively simple porins to large and complex molecules such as autotransporters, intimins, and invasins. The canonical structure for the membrane-embedded domain of these proteins is a beta-barrel, composed of antiparallel beta-strands. After synthesis in the cytoplasm, beta-barrel proteins reach the periplasm in an unfolded state, and are then folded and inserted into the outer membrane by the beta-barrel assembly machinery (BAM, fig. 1; Knowles et al. 2009; Hagan et al. 2011; Selkrig et al. 2013). The BAM complex in Escherichia coli consists of five subunits, BamA–E (fig. 1). BamA is essential (Genevrois et al. 2003; Voulhoux et al. 2003) and is found in all Gram-negative bacteria (Heinz and Lithgow 2014). As a member of the Omp85 protein family, BamA is itself a membrane-embedded beta-barrel protein (Noinaj et al. 2013) with several periplasmic polypeptide transport-associated (POTRA) domains (fig. 1). BamD, the other component essential in Proteobacteria, has also been identified in other groups of bacteria (Anwari et al. 2012; Webb et al. 2012), whereas other components of the BAM complex in E. coli, BamB, BamC, and BamE are outer membrane lipoproteins found only in subsets of the Proteobacteria (Anwari et al. 2012; Webb et al. 2012).Fig. 1.—

Bottom Line: We report that TamA and a closely related protein TamL are confined almost exclusively to Proteobacteria and Bacteroidetes/Chlorobi respectively, whereas TamB is widely distributed across the majority of Gram-negative bacterial lineages.Several sequence characteristics were discovered to define the TamB protein family: A signal-anchor linkage to the inner membrane, beta-helical structure, conserved domain architecture and a C-terminal region that mimics outer membrane protein beta-strands.Taken together, the structural and phylogenetic analyses suggest that the TAM likely evolved from an original combination of BamA and TamB, with a later gene duplication event of BamA, giving rise to an additional Omp85 sequence that evolved to be TamA in Proteobacteria and TamL in Bacteroidetes/Chlorobi.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Monash University, Melbourne, Victoria, Australia.

Show MeSH