Crystal structure and functional analysis of Escherichia coli glutamate decarboxylase

Guido Capitani, Daniela De Biase, Caterina Aurizi, Heinz Gut, Francesco Bossa, Markus G. Grütter

Research output: Contribution to journalArticlepeer-review


Glutamate decarboxylase is a vitamin B6-dependent enzyme, which catalyses the decarboxylation of glutamate to γ-aminobutyrate. In Escherichia coli, expression of glutamate decarboxylase (GadB), a 330 kDa hexamer, is induced to maintain the physiological pH under acidic conditions, like those of the passage through the stomach en route to the intestine. GadB, together with the antiporter GadC, constitutes the gad acid resistance system, which confers the ability for bacterial survival for at least 2 h in a strongly acidic environment. GadB undergoes a pH-dependent conformational change and exhibits an activity optimum at low pH. We determined the crystal structures of GadB at acidic and neutral pH. They reveal the molecular details of the conformational change and the structural basis for the acidic pH optimum. We demonstrate that the enzyme is localized exclusively in the cytoplasm at neutral pH, but is recruited to the membrane when the pH falls. We show by structure-based site-directed mutagenesis that the triple helix bundle formed by the N-termini of the protein at acidic pH is the major determinant for this behaviour.

Original languageEnglish
Pages (from-to)4027-4037
Number of pages11
JournalEMBO Journal
Issue number16
Publication statusPublished - Aug 15 2003


  • Bacterial acid resistance
  • Cellular localization
  • Escherichia coli
  • Glutamate decarboxylase
  • Pyridoxal 5′-phosphate

ASJC Scopus subject areas

  • Genetics
  • Cell Biology


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