We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Escherichia coli acid resistance: pH-sensing, activation by chloride and autoinhibition in GadB.
- Authors
Gut, Heinz; Pennacchietti, Eugenia; John, Robert A; Bossa, Francesco; Capitani, Guido; De Biase, Daniela; Grütter, Markus G
- Abstract
Escherichia coli and other enterobacteria exploit the H+ -consuming reaction catalysed by glutamate decarboxylase to survive the stomach acidity before reaching the intestine. Here we show that chloride, extremely abundant in gastric secretions, is an allosteric activator producing a 10-fold increase in the decarboxylase activity at pH 5.6. Cooperativity and sensitivity to chloride were lost when the N-terminal 14 residues, involved in the formation of two triple-helix bundles, were deleted by mutagenesis. X-ray structures, obtained in the presence of the substrate analogue acetate, identified halide-binding sites at the base of each N-terminal helix, showed how halide binding is responsible for bundle stability and demonstrated that the interconversion between active and inactive forms of the enzyme is a stepwise process. We also discovered an entirely novel structure of the cofactor pyridoxal 5'-phosphate (aldamine) to be responsible for the reversibly inactivated enzyme. Our results link the entry of chloride ions, via the H+/Cl- exchange activities of ClC-ec1, to the trigger of the acid stress response in the cell when the intracellular proton concentration has not yet reached fatal values.
- Publication
The EMBO journal, 2006, Vol 25, Issue 11, p2643
- ISSN
0261-4189
- Publication type
Journal Article
- DOI
10.1038/sj.emboj.7601107