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Modeling ToxT to explain how cholera toxicity can be regulated by fatty acids: The 2014 Pingry SMART Team project (946.7)

Infections of the enteric bacterium Vibrio cholerae cause the disease cholera and lead to severe dehydration and even death to those who ingest water contaminated with the organism. Two virulence factors are required for infection: the toxin‐corregulated pilus (TCP) and cholera toxin (CT). The production of both gene products is regulated by the transcription factor ToxT, a member of the AraC protein family. The structure of ToxT was solved by X‐ray crystallography and revealed a 16‐carbon fatty acid, cis‐palmitoleate, in the ligand binding pocket of the protein’s regulatory domain. Further analysis indicated that expression of both TCP and CT were reduced in the presence of cis‐palmitoleate and that binding of the fatty acid to ToxT prevented DNA binding and led to a reduction in virulence factor expression. Using the structure determined in this study, The Pingry School SMART (Students Modeling A Research Topic) Team, is using a 3D‐printer from the Milwaukee School of Engineering (MSOE) to model the interactions between ToxT and cis‐palmitoleate. Ligand binding by the regulatory domain of the ToxT leads to a change in conformation of the DNA‐binding domain, resulting in decreased interaction with DNA. Fatty acid regulation of ToxT‐DNA binding provides insight into the mechanism of controlling virulence gene expression in V. cholerae. Studies based on this research are currently investigating the structure and function of other AraC‐family members from a variety of infectious bacteria, seeking to determine if fatty acids may also be involved in regulation of virulence factor expression in other organisms.