Characterization of the ligand binding pocket of the virulence regulator Rns, a member of the AraC/XylS family of transcription factors

As antimicrobial resistance increases, it is critical to develop new strategies to combat these infections. One area of concern is bacteria that cause intestinal disease such as <i>Salmonella</i> species, <i>Vibrio cholerae</i>, <i>Shigella</i> species, and enterotoxigenic <i>Escherichia coli</i> (ETEC). ETEC is a leading cause of travelers' diarrheal disease and a leading cause of mortality for children under 5 years old. To cause disease, ETEC requires the gene regulator Rns. Our previous work found that Rns was inhibited by a fatty acid. Here, we identify key features in the protein that are required for not only binding fatty acids but also for responding to them. This was done through a combination of microbiological as well as structural techniques of altered Rns proteins that can no longer bind fatty acid. Understanding how Rns is inhibited will lead to new ideas about how to target this class of proteins without causing antimicrobial resistance.