PMID: 19478139 , Related PDB ids: 3H5M, 3H6B

Authors:

Gao X, Lu F, Zhou L, Dang S, Sun L, Li X, Wang J, Shi Y

Title:

Structure and mechanism of an amino acid antiporter.

Journal:

Science. 2009 Jun 19;324(5934):1565-8. Epub 2009 May 28.

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.