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Phylogenetic analysis of Shiga toxin 1 and Shiga toxin 2 genes associated with disease outbreaks.

Lee JE, Reed J, Shields MS, Spiegel KM, Farrell LD, Sheridan PP - BMC Microbiol. (2007)

Bottom Line: The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1.The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time.These data could indicate that Shiga toxins are experiencing purifying selection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Idaho State University, 921 South 8th Ave,, Pocatello, ID 83209-8007, USA. james.e.lee@amedd.army.mil

ABSTRACT

Background: Shiga toxins 1 and 2 (Stx1 and Stx2) are bacteriophage-encoded proteins that have been associated with hemorrhagic colitis, hemolytic uremic syndrome and other severe disease conditions. Stx1 and Stx2 are genetically and immunologically distinct but share the same compound toxin structure, method of entry and enzymatic function.

Results: Phylogenetic analysis was performed using Stx1 and Stx2 amino acid and nucleotide sequences from 41 strains of Escherichia coli, along with known stx sequences available from GenBank. The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1. The phylograms showed generally flat topologies among our strains' stx1 and stx2 genes. In the stx2 gene, 39.5% of the amino acid sites display very low nonsynonymous to synonymous substitution ratios.

Conclusion: The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time. These data could indicate that Shiga toxins are experiencing purifying selection.

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Related in: MedlinePlus

Stx1 A and B Subunit Amino Acid Alignment. Sequences that are identical are on the same line and are pipe-delimited.
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Figure 1: Stx1 A and B Subunit Amino Acid Alignment. Sequences that are identical are on the same line and are pipe-delimited.

Mentions: The Shiga Toxin 1 A and B subunit genes showed very little difference in amino acid sequence (Figure 1). There were only four amino acid differences among the stx1 genes in the entire alignment. The change from threonine to serine at A67 in strains H19, BCL17 and I6650 would predictably have little effect on the enzymatic activity of the A subunit. The B354 change from threonine to serine in 88–1509 and the B357 change from valine to alanine in H19 are also unlikely to change the binding function of the B subunit.


Phylogenetic analysis of Shiga toxin 1 and Shiga toxin 2 genes associated with disease outbreaks.

Lee JE, Reed J, Shields MS, Spiegel KM, Farrell LD, Sheridan PP - BMC Microbiol. (2007)

Stx1 A and B Subunit Amino Acid Alignment. Sequences that are identical are on the same line and are pipe-delimited.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211750&req=5

Figure 1: Stx1 A and B Subunit Amino Acid Alignment. Sequences that are identical are on the same line and are pipe-delimited.
Mentions: The Shiga Toxin 1 A and B subunit genes showed very little difference in amino acid sequence (Figure 1). There were only four amino acid differences among the stx1 genes in the entire alignment. The change from threonine to serine at A67 in strains H19, BCL17 and I6650 would predictably have little effect on the enzymatic activity of the A subunit. The B354 change from threonine to serine in 88–1509 and the B357 change from valine to alanine in H19 are also unlikely to change the binding function of the B subunit.

Bottom Line: The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1.The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time.These data could indicate that Shiga toxins are experiencing purifying selection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Idaho State University, 921 South 8th Ave,, Pocatello, ID 83209-8007, USA. james.e.lee@amedd.army.mil

ABSTRACT

Background: Shiga toxins 1 and 2 (Stx1 and Stx2) are bacteriophage-encoded proteins that have been associated with hemorrhagic colitis, hemolytic uremic syndrome and other severe disease conditions. Stx1 and Stx2 are genetically and immunologically distinct but share the same compound toxin structure, method of entry and enzymatic function.

Results: Phylogenetic analysis was performed using Stx1 and Stx2 amino acid and nucleotide sequences from 41 strains of Escherichia coli, along with known stx sequences available from GenBank. The analysis confirmed the Stx1 and Stx2 divergence, and showed that there is generally more sequence variation among stx2 genes than stx1. The phylograms showed generally flat topologies among our strains' stx1 and stx2 genes. In the stx2 gene, 39.5% of the amino acid sites display very low nonsynonymous to synonymous substitution ratios.

Conclusion: The stx1 and stx2 genes used in this phylogenetic study show sequence conservation with no significant divergence with respect to place or time. These data could indicate that Shiga toxins are experiencing purifying selection.

Show MeSH
Related in: MedlinePlus