title: Virstatin inhibits dimerization of the transcriptional activator ToxT.
abstract: The development of antimicrobials is critical in this time of increasing antibiotic resistance of most clinically relevant bacteria. To date, all current antibiotics focus on inhibiting crucial enzymatic activities of their protein targets (i.e., trimethoprim for dihydrofolate reductase), thus disrupting in vitro essential gene functions. In contrast, we have previously reported the identification of virstatin, a small molecule that inhibits virulence regulation in Vibrio cholerae, thereby preventing intestinal colonization in an infant mouse model for cholera. Virstatin prevents expression of the two major V. cholerae virulence factors, cholera toxin (CT) and the toxin coregulated pilus, by inhibiting the virulence transcriptional activator ToxT. It has previously been described that the N-terminal domain of ToxT has the ability to form homodimers. We now demonstrate that virstatin inhibits ToxT dimerization, thus demonstrating that it further falls into a unique class of inhibitors that works by disrupting protein-protein interactions, particularly homodimerization. Using virstatin, truncation mutants of ToxT, and a virstatin-resistant mutant, we show that dimerization is required for ToxT activation of the ctx promoter. In contrast, ToxT dimerization does not appear to be required at all of the other ToxT-regulated promoters, suggesting multiple mechanisms may exist for its transcriptional activity.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, Armenise Building, Room 425, 200 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Shakhnovich
authors.forename: Deborah T
authors.initials: DT
authors.lastname: Hung
authors.forename: Emily
authors.initials: E
authors.lastname: Pierson
authors.forename: Kyungae
authors.initials: K
authors.lastname: Lee
authors.forename: John J
authors.initials: JJ
authors.lastname: Mekalanos
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000187:drug effects; D002087:Butyrates / Q000494:pharmacology*; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D009281:Naphthalenes / Q000494:pharmacology*; D053644:Naphthalimides / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D015534:Trans-Activators / Q000187:drug effects*; D014157:Transcription Factors / Q000187:drug effects; D014734:Vibrio cholerae
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002087:Butyrates; D009281:Naphthalenes; D053644:Naphthalimides; D015534:Trans-Activators; D014157:Transcription Factors; C505381:virstatin; C075626:tcpN protein, Vibrio cholerae