4dji | pdb_00004dji

Structure of glutamate-GABA antiporter GadC

spinqualitylabelsall models 4dji, resolution 3.19Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4dji is a 2 chain structure with sequence from Escherichia coli K-12. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [GADC_ECOLI] Involved in glutamate-dependent acid resistance. Imports glutamate inside the cell while simultaneously exporting to the periplasm the GABA produced by GadA and GadB. The gad system helps to maintain a near-neutral intracellular pH when cells are exposed to extremely acidic conditions. The ability to survive transit through the acidic conditions of the stomach is essential for successful colonization of the mammalian host by commensal and pathogenic bacteria. Publication Abstract from PubMed Food-borne hemorrhagic Escherichia coli, exemplified by the strains O157:H7 and O104:H4 (refs 1, 2), require elaborate acid-resistance systems (ARs) to survive the extremely acidic environment such as the stomach (pH approximately 2). AR2 expels intracellular protons through the decarboxylation of L-glutamate (Glu) in the cytoplasm and exchange of the reaction product gamma-aminobutyric acid (GABA) with extracellular Glu. The latter process is mediated by the Glu-GABA antiporter GadC, a representative member of the amino-acid-polyamine-organocation superfamily of membrane transporters. The functional mechanism of GadC remains largely unknown. Here we show, with the use of an in vitro proteoliposome-based assay, that GadC transports GABA/Glu only under acidic conditions, with no detectable activity at pH values higher than 6.5. We determined the crystal structure of E. coli GadC at 3.1 A resolution under basic conditions. GadC, comprising 12 transmembrane segments (TMs), exists in a closed state, with its carboxy-terminal domain serving as a plug to block an otherwise inward-open conformation. Structural and biochemical analyses reveal the essential transport residues, identify the transport path and suggest a conserved transport mechanism involving the rigid-body rotation of a helical bundle for GadC and other amino acid antiporters. Structure and mechanism of a glutamate-GABA antiporter.,Ma D, Lu P, Yan C, Fan C, Yin P, Wang J, Shi Y Nature. 2012 Mar 11;483(7391):632-6. doi: 10.1038/nature10917. PMID:22407317 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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