2DGK

Crystal structure of an N-terminal deletion mutant of Escherichia coli GadB in an autoinhibited state (aldamine)

Summary for 2DGK

• Entry DOI: 10.2210/pdb2dgk/pdb
• Related: 1PMM 1PMO 2DGL 2DGM
• Descriptor: Glutamate decarboxylase beta, SULFATE ION, PYRIDOXAL-5'-PHOSPHATE, ... (5 entities in total)
• Functional Keywords: gadb, gadbd1-14, autoinhibition, substituted aldamine, lyase
• Biological source: Escherichia coli
• Cellular location: Cytoplasm: P69910
• Total number of polymer chains: 6
• Total formula weight: 308957.87

Authors

Gruetter, M.G.,Capitani, G.,Gut, H. (deposition date: 2006-03-14, release date: 2006-06-20, Last modification date: 2023-10-25)

Primary citation

Gut, H.,Pennacchietti, E.,John, R.A.,Bossa, F.,Capitani, G.,De Biase, D.,Gruetter, M.G.
Escherichia coli acid resistance: pH-sensing, activation by chloride and autoinhibition in GadB
Embo J., 25:2643-2651, 2006

PubMed 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.

PubMed: 16675957
DOI: 10.1038/sj.emboj.7601107

Experimental method

X-RAY DIFFRACTION (1.9 Å)