Horizontally acquired HosA transcription factor bound with 4-hydroxy-benzoic acid exhibits unique tug-of-water dynamics

Pathogenic Escherichia coli (E. coli) causes serious illnesses in humans aided by several multiple antibiotic resistance regulator (MarR) transcription factors. Among these proteins, HosA provides support to these organisms by executing crucial roles in functions ranging from flagella motility to organic compound metabolism. The crystal structure of HosA from enteropathogenic E. coli is elucidated in this study along with conformational changes orchestrated by different amino acids due to para-hydroxy benzoic acid (PHB) binding in the hinge region. Structural analysis and extensive molecular dynamics simulation reveal role of a dynamic water molecule as a bridging entity in PHB bound structure which is not shown for any MarR structure yet. Also, it is shown that the HosA gene is transferred horizontally from Shigella to pathogenic E. coli, having 97.6% sequence similarity with an uncharacterized transcription factor from Shigella dysenteriae Sd197. This study may be promising to address several unanswered questions for the functioning of MarR transcription factors from infectious E. coli and design inhibitors to combat these pathogens.