Abstract
The yfdX family proteins are known for long time to occur in various virulent bacteria including their multidrug resistant (MDR) strains, without any direct assigned function for them. However, yfdX protein along with other proteins involved in acid tolerance response is reported to be up regulated by the multidrug response regulatory system in E. coli. Hence, molecular and functional characterization of this protein is important for understanding of key cellular processes in bacterial cells. Here we study STY3178, a yfdX protein from a MDR strain of typhoid fever causing Salmonella Typhi. Our experimental results indicate that STY3178 is a helical protein existing in a trimeric oligomerization state in solution. We also observe many small antibiotics, like ciprofloxacin, rifampin and ampicillin viably interact with this protein. The dissociation constants from the quenching of steady state fluorescence and isothermal titration calorimetry show that ciprofloxacin binding is stronger than rifampin followed by ampicillin.
Highlights
The yfdX family proteins are known for long time to occur in various virulent bacteria including their multidrug resistant (MDR) strains, without any direct assigned function for them
The questions of our interest are the following: (i) Is STY3178 an oligomeric protein in solution given that its orthologue from K. pneumoniae has a tetrameric structure as reported? (ii) Is STY3178 capable of binding drugs or antibiotic molecules? In solution we find STY3178 is a well-folded primarily α -helical protein like its orthologue
Recombinant 6-His-tagged protein is expressed successfully in E. coli which migrates in SDS-PAGE around ~25 KDa as shown in Fig. 1a
Summary
The yfdX family proteins are known for long time to occur in various virulent bacteria including their multidrug resistant (MDR) strains, without any direct assigned function for them. YfdX protein along with other proteins involved in acid tolerance response is reported to be up regulated by the multidrug response regulatory system in E. coli. We study STY3178, a yfdX protein from a MDR strain of typhoid fever causing Salmonella Typhi. Among the DUF proteins, the yfdX protein family is a prominent member These yfdX proteins have orthologues identified in many virulent bacteria, such as E. coli, S. Occurrence of yfdX proteins in disease-causing bacteria and its co-expression along with the multidrug response regulator protein in E. coli indicates that this protein probably has functional role in bacteria which is hitherto unknown. Dynamic light scattering (DLS), size exclusion chromatography (SEC) and nuclear www.nature.com/scientificreports/
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