Structure and mechanism of an amino acid antiporter.
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Gao X, Lu F, Zhou L, Dang S, Sun L, Li X, Wang J, Shi Y
Structure and mechanism of an amino acid antiporter.
Science. 2009 Jun 19;324(5934):1565-8. doi: 10.1126/science.1173654. Epub 2009 May 28.
- PubMed ID
- 19478139 [ View in PubMed]
- Abstract
Virulent enteric pathogens such as Escherichia coli strain O157:H7 rely on acid-resistance (AR) systems to survive the acidic environment in the stomach. A major component of AR is an arginine-dependent arginine:agmatine antiporter that expels intracellular protons. Here, we report the crystal structure of AdiC, the arginine:agmatine antiporter from E. coli O157:H7 and a member of the amino acid/polyamine/organocation (APC) superfamily of transporters at 3.6 A resolution. The overall fold is similar to that of several Na+-coupled symporters. AdiC contains 12 transmembrane segments, forms a homodimer, and exists in an outward-facing, open conformation in the crystals. A conserved, acidic pocket opens to the periplasm. Structural and biochemical analysis reveals the essential ligand-binding residues, defines the transport route, and suggests a conserved mechanism for the antiporter activity.