4IU9: Crystal Structure Of A Membrane Transporter

The nitrate/nitrite transporters NarK and NarU play an important role in nitrogen homeostasis in bacteria and belong to the nitrate/nitrite porter family (NNP) of the major facilitator superfamily (MFS) fold. The structure and functional mechanism of NarK and NarU remain unknown. Here, we report the crystal structure of NarU at a resolution of 3.1 A and systematic biochemical characterization. The two molecules of NarU in an asymmetric unit exhibit two distinct conformational states: occluded and partially inward-open. The substrate molecule nitrate appears to be coordinated by four highly conserved, charged, or polar amino acids. Structural and biochemical analyses allowed the identification of key amino acids that are involved in substrate gating and transport. The observed conformational differences of NarU, together with unique sequence features of the NNP family transporters, suggest a transport mechanism that might deviate from the canonical rocker-switch model.
PDB ID: 4IU9Download
MMDB ID: 109230
PDB Deposition Date: 2013/1/20
Updated in MMDB: 2013/04
Experimental Method:
x-ray diffraction
Resolution: 3  Å
Source Organism:
Similar Structures:
Biological Unit for 4IU9: monomeric; determined by author and by software (PISA)
Molecular Components in 4IU9
Label Count Molecule
Protein (1 molecule)
Nitrite Extrusion Protein 2(Gene symbol: narU)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB