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Science. 2005 Aug 12;309(5737):1093-6.

Structural basis for the activation of cholera toxin by human ARF6-GTP.

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Department of Chemistry, University of Washington, Seattle, WA 98195, USA.


The Vibrio cholerae bacterium causes devastating diarrhea when it infects the human intestine. The key event is adenosine diphosphate (ADP)-ribosylation of the human signaling protein GSalpha, catalyzed by the cholera toxin A1 subunit (CTA1). This reaction is allosterically activated by human ADP-ribosylation factors (ARFs), a family of essential and ubiquitous G proteins. Crystal structures of a CTA1:ARF6-GTP (guanosine triphosphate) complex reveal that binding of the human activator elicits dramatic changes in CTA1 loop regions that allow nicotinamide adenine dinucleotide (NAD+) to bind to the active site. The extensive toxin:ARF-GTP interface surface mimics ARF-GTP recognition of normal cellular protein partners, which suggests that the toxin has evolved to exploit promiscuous binding properties of ARFs.

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