NDLI: Mechanism for Inhibition of Vibrio cholerae ToxT Activity by the Unsaturated Fatty Acid Components of Bile

Content Provider	PubMed Central
Author	Plecha, Sarah C. Withey, Jeffrey H.
Editor	Dirita, V. J.
Copyright Year	2015
Abstract	The Gram-negative curved bacillus Vibrio cholerae causes the severe diarrheal illness cholera. During host infection, a complex regulatory cascade results in production of ToxT, a DNA-binding protein that activates the transcription of major virulence genes that encode cholera toxin (CT) and toxin-coregulated pilus (TCP). Previous studies have shown that bile and its unsaturated fatty acid (UFA) components reduce virulence gene expression and therefore are likely important signals upon entering the host. However, the mechanism for the bile-mediated reduction of TCP and CT expression has not been clearly defined. There are two likely hypotheses to explain this reduction: (i) UFAs decrease DNA binding by ToxT, or (ii) UFAs decrease dimerization of ToxT. The work presented here elucidates that bile or UFAs directly affect DNA binding by ToxT. UFAs, specifically linoleic acid, can enter V. cholerae when added exogenously and are present in the cytoplasm, where they can then interact with ToxT. Electrophoretic mobility shift assays (EMSAs) with ToxT and various virulence promoters in the presence or absence of UFAs showed a direct reduction in ToxT binding to DNA, even in promoters with only one ToxT binding site. Virstatin, a synthetic ToxT inhibitor, was previously shown to reduce ToxT dimerization. Here we show that virstatin affects DNA binding only at ToxT promoters with two binding sites, unlike linoleic acid, which affects ToxT binding promoters having either one or two ToxT binding sites. This suggests a mechanism in which UFAs, unlike virstatin, do not affect dimerization but affect monomeric ToxT binding to DNA.
Related Links	http://dx.doi.org/10.1128/jb.02409-14
Ending Page	1725
Page Count	10
Starting Page	1716
File Format	PDF
ISSN	00219193
e-ISSN	10985530
Journal	Journal of Bacteriology
Issue Number	10
Volume Number	197
Language	English
Publisher	American Society for Microbiology
Publisher Date	2015-05-15
Access Restriction	Open
Rights Holder	American Society for Microbiology
Subject Keyword	Molecular Biology Microbiology Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Molecular Biology Microbiology

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