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The bacterial intimins and invasins: a large and novel family of secreted proteins.

Tsai JC, Yen MR, Castillo R, Leyton DL, Henderson IR, Saier MH - PLoS ONE (2010)

Bottom Line: Proteins belonging to this family are predominantly associated with organisms from the γ-proteobacteria.However, all repeated subdomains are found in tandem, suggesting that subdomain shuffling occurred rarely if at all.This study is the first of its kind to describe this unusual family of bacterial adhesins.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, University of California at San Diego, La Jolla, California, United States of America.

ABSTRACT

Background: Gram-negative bacteria have developed a limited repertoire of solutions for secreting proteins from the cytoplasmic compartment to the exterior of the cell. Amongst the spectrum of secreted proteins are the intimins and invasins (the Int/Inv family; TC# 1.B.54) which are characterized by an N-terminal β-barrel domain and a C-terminal surface localized passenger domain. Despite the important role played by members of this family in diseases mediated by several species of the Enterobacteriaceae, there has been little appreciation for the distribution and diversity of these proteins amongst Gram-negative bacteria. Furthermore, there is little understanding of the molecular events governing secretion of these proteins to the extracellular milieu.

Principal findings: In silico approaches were used to analyze the domain organization and diversity of members of this secretion family. Proteins belonging to this family are predominantly associated with organisms from the γ-proteobacteria. Whilst proteins from the Chlamydia, γ-, β- and ε-proteobacteria possess β-barrel domains and passenger domains of various sizes, Int/Inv proteins from the α-proteobacteria, cyanobacteria and chlorobi possess only the predicted β-barrel domains. Phylogenetic analyses revealed that with few exceptions these proteins cluster according to organismal type, indicating that divergence occurred contemporaneously with speciation, and that horizontal transfer was limited. Clustering patterns of the β-barrel domains correlate well with those of the full-length proteins although the passenger domains do so with much less consistency. The modular subdomain design of the passenger domains suggests that subdomain duplication and deletion have occurred with high frequency over evolutionary time. However, all repeated subdomains are found in tandem, suggesting that subdomain shuffling occurred rarely if at all. Topological predictions for the β-barrel domains are presented.

Conclusion: Based on our in silico analyses we present a model for the biogenesis of these proteins. This study is the first of its kind to describe this unusual family of bacterial adhesins.

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Related in: MedlinePlus

Average hydropathy, amphipathicity, and similarity plots for the β-barrel domains of the 69 Intimin/Invasin proteins included in this study.The plots were generated with the AveHAS program [38]. A window size of 9 residues with the angle set at 180° was used as is appropriate for β-strand analyses. Average hydropathy, dark solid line, middle; Average amphipathicity, faint solid line, top; Average similarity, dashed line, bottom. These plots present relative values as a function of alignment position for all three characteristics.
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pone-0014403-g005: Average hydropathy, amphipathicity, and similarity plots for the β-barrel domains of the 69 Intimin/Invasin proteins included in this study.The plots were generated with the AveHAS program [38]. A window size of 9 residues with the angle set at 180° was used as is appropriate for β-strand analyses. Average hydropathy, dark solid line, middle; Average amphipathicity, faint solid line, top; Average similarity, dashed line, bottom. These plots present relative values as a function of alignment position for all three characteristics.

Mentions: Despite the amino acid sequence conservation, pore-forming ability and the critical nature of the β-domain for biogenesis, the precise topological organization of the β-barrel domain remains undetermined. The multiple alignment shown in Fig. S2 for the β-barrel domains was used to derive average hydropathy, amphipathicity and similarity plots (Fig. 5). Sixteen peaks of average hydrophobicity coincide with 16 peaks of average similarity, and all of these peaks overlap peaks of amphipathicity (Fig. 5). These characteristics suggest that there may be as many as 16 transmembrane β-strands comprising these barrels.


The bacterial intimins and invasins: a large and novel family of secreted proteins.

Tsai JC, Yen MR, Castillo R, Leyton DL, Henderson IR, Saier MH - PLoS ONE (2010)

Average hydropathy, amphipathicity, and similarity plots for the β-barrel domains of the 69 Intimin/Invasin proteins included in this study.The plots were generated with the AveHAS program [38]. A window size of 9 residues with the angle set at 180° was used as is appropriate for β-strand analyses. Average hydropathy, dark solid line, middle; Average amphipathicity, faint solid line, top; Average similarity, dashed line, bottom. These plots present relative values as a function of alignment position for all three characteristics.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3008723&req=5

pone-0014403-g005: Average hydropathy, amphipathicity, and similarity plots for the β-barrel domains of the 69 Intimin/Invasin proteins included in this study.The plots were generated with the AveHAS program [38]. A window size of 9 residues with the angle set at 180° was used as is appropriate for β-strand analyses. Average hydropathy, dark solid line, middle; Average amphipathicity, faint solid line, top; Average similarity, dashed line, bottom. These plots present relative values as a function of alignment position for all three characteristics.
Mentions: Despite the amino acid sequence conservation, pore-forming ability and the critical nature of the β-domain for biogenesis, the precise topological organization of the β-barrel domain remains undetermined. The multiple alignment shown in Fig. S2 for the β-barrel domains was used to derive average hydropathy, amphipathicity and similarity plots (Fig. 5). Sixteen peaks of average hydrophobicity coincide with 16 peaks of average similarity, and all of these peaks overlap peaks of amphipathicity (Fig. 5). These characteristics suggest that there may be as many as 16 transmembrane β-strands comprising these barrels.

Bottom Line: Proteins belonging to this family are predominantly associated with organisms from the γ-proteobacteria.However, all repeated subdomains are found in tandem, suggesting that subdomain shuffling occurred rarely if at all.This study is the first of its kind to describe this unusual family of bacterial adhesins.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, University of California at San Diego, La Jolla, California, United States of America.

ABSTRACT

Background: Gram-negative bacteria have developed a limited repertoire of solutions for secreting proteins from the cytoplasmic compartment to the exterior of the cell. Amongst the spectrum of secreted proteins are the intimins and invasins (the Int/Inv family; TC# 1.B.54) which are characterized by an N-terminal β-barrel domain and a C-terminal surface localized passenger domain. Despite the important role played by members of this family in diseases mediated by several species of the Enterobacteriaceae, there has been little appreciation for the distribution and diversity of these proteins amongst Gram-negative bacteria. Furthermore, there is little understanding of the molecular events governing secretion of these proteins to the extracellular milieu.

Principal findings: In silico approaches were used to analyze the domain organization and diversity of members of this secretion family. Proteins belonging to this family are predominantly associated with organisms from the γ-proteobacteria. Whilst proteins from the Chlamydia, γ-, β- and ε-proteobacteria possess β-barrel domains and passenger domains of various sizes, Int/Inv proteins from the α-proteobacteria, cyanobacteria and chlorobi possess only the predicted β-barrel domains. Phylogenetic analyses revealed that with few exceptions these proteins cluster according to organismal type, indicating that divergence occurred contemporaneously with speciation, and that horizontal transfer was limited. Clustering patterns of the β-barrel domains correlate well with those of the full-length proteins although the passenger domains do so with much less consistency. The modular subdomain design of the passenger domains suggests that subdomain duplication and deletion have occurred with high frequency over evolutionary time. However, all repeated subdomains are found in tandem, suggesting that subdomain shuffling occurred rarely if at all. Topological predictions for the β-barrel domains are presented.

Conclusion: Based on our in silico analyses we present a model for the biogenesis of these proteins. This study is the first of its kind to describe this unusual family of bacterial adhesins.

Show MeSH
Related in: MedlinePlus