Abstract
The molecular basis for the survival of bacteria under extreme conditions in which growth is inhibited is a question of great current interest. A preliminary study was carried out to determine residue pattern conservation among the antiporters of enteric bacteria, responsible for extreme acid sensitivity especially in Escherichia coli and Shigella flexneri. Here we found the molecular evidence that proved the relationship between E. coli and S. flexneri. Multiple sequence alignment of the gadC coded acid sensitive antiporter showed many conserved residue patterns at regular intervals at the N-terminal region. It was observed that as the alignment approaches towards the C-terminal, the number of conserved residues decreases, indicating that the N-terminal region of this protein has much active role when compared to the carboxyl terminal. The motif, FHLVFFLLLGG, is well conserved within the entire gadC coded protein at the amino terminal. The motif is also partially conserved among other antiporters (which are not coded by gadC) but involved in acid sensitive/resistance mechanism. Phylogenetic cluster analysis proves the relationship of Escherichia coli and Shigella flexneri. The gadC coded proteins are converged as a clade and diverged from other antiporters belongs to the amino acid-polyamine-organocation (APC) superfamily.
Highlights
Microbes are not always boned to have the favorable condition for their survival
The gad system is based on the coordinated action of these two homologues of glutamate decarboxylase and of a specific glutamate/gamma-aminobutyrate antiporter (GadC) [4], in which glutamate is internalized and converted to γaminobutyrate that is subsequently exchanged for another extracellular glutamate via a membrane-located antiporter
Distinct pattern conservation of glutamate binding region Multiple alignment of the gadC coded acid sensitive antiporter showed many conserved residue patterns in a regular interval at the N-terminal region and as the alignment approached the C-terminal end, the number of conserved residues decreased, indicating that the Nterminal region of this protein has a much active role when compared to the carboxyl terminal end
Summary
Microbes are not always boned to have the favorable condition for their survival. So as to tackle the unfavorable conditions, they adopt certain mechanisms to overcome it. This high similarity may be convergence of gadC coded antiporters stands separately from due to the two glutamate decarboxylases, encoded by gadA other antiporters which comprises of Listeria monocytogenes, and gadB, with gadB forming part of an operon with the Clostridium perfringens, Lactococcus lactis E. coli, S. flexneri antiporter determinant gadC. Our pattern analysis shows the relationship of Escherichia coli and Shigella flexneri This can be correlated with the claims of Waterman and Small (2003) [19], for a strong-link between the possession of the gadC genes and the expression of stationary-phase acid resistance.
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