Editors' ChoiceBiochemistry

Antiporter Antics

Science Signaling  23 Jun 2009:
Vol. 2, Issue 76, pp. ec211
DOI: 10.1126/scisignal.276ec211

Bacteria that survive in the acidic environment of the stomach have mechanisms to maintain a high intracellular pH. In Escherichia coli, glutamate (Glu) and arginine (Arg) are decarboxylated intracellularly and the reaction products are exchanged with extracellular Glu and Arg. Gao et al. now report a crystal structure of AdiC, an arginine:agmatine antiporter from E. coli. AdiC exhibits the same fold as that of the Na+-coupled symporters, including LeuT. It contains 12 transmembrane segments, forms a homodimer, and exists in an outward-facing, open conformation in the crystals. The structure, together with biochemical data, suggests how the antiporter senses the pH and responds to transport the reaction product agmatine out of the cell and Arg into the cell.

X. Gao, F. Lu, L. Zhou, S. Dang, L. Sun, X. Li, J. Wang, Y. Shi, Structure and mechanism of an amino acid antiporter. Science 324, 1565–1568 (2009). [Abstract] [Full Text]