3NCY: X-Ray Crystal Structure Of An Arginine Agmatine Antiporter (Adic) In Complex With A Fab Fragment

To reach the mammalian gut, enteric bacteria must pass through the stomach. Many such organisms survive exposure to the harsh gastric environment (pH 1.5-4) by mounting extreme acid-resistance responses, one of which, the arginine-dependent system of Escherichia coli, has been studied at levels of cellular physiology, molecular genetics and protein biochemistry. This multiprotein system keeps the cytoplasm above pH 5 during acid challenge by continually pumping protons out of the cell using the free energy of arginine decarboxylation. At the heart of the process is a 'virtual proton pump' in the inner membrane, called AdiC, that imports L-arginine from the gastric juice and exports its decarboxylation product agmatine. AdiC belongs to the APC superfamily of membrane proteins, which transports amino acids, polyamines and organic cations in a multitude of biological roles, including delivery of arginine for nitric oxide synthesis, facilitation of insulin release from pancreatic beta-cells, and, when inappropriately overexpressed, provisioning of certain fast-growing neoplastic cells with amino acids. High-resolution structures and detailed transport mechanisms of APC transporters are currently unknown. Here we describe a crystal structure of AdiC at 3.2 A resolution. The protein is captured in an outward-open, substrate-free conformation with transmembrane architecture remarkably similar to that seen in four other families of apparently unrelated transport proteins.
PDB ID: 3NCYDownload
MMDB ID: 84211
PDB Deposition Date: 2010/6/6
Updated in MMDB: 2010/08
Experimental Method:
x-ray diffraction
Resolution: 3.2  Å
Source Organism:
Salmonella enterica subsp. enterica serovar Typhimurium
Similar Structures:
Biological Unit for 3NCY: tetrameric; determined by author
Molecular Components in 3NCY
Label Count Molecule
Proteins (4 molecules)
Adic(Gene symbol: yjdE)
Molecule annotation
FAB Heavy Chain
Molecule annotation
FAB Light Chain
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB