4FC4 image
Entry Detail
PDB ID:
4FC4
Title:
FNT family ion channel
Biological Source:
PDB Version:
Deposition Date:
2012-05-24
Release Date:
2012-11-21
Method Details:
Experimental Method:
Resolution:
2.40 Å
R-Value Free:
0.23
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
C 1 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Nitrite transporter NirC
Chain IDs:A, B, C, D, E, F, G, H, I, J
Chain Length:261
Number of Molecules:10
Biological Source:Salmonella enterica subsp. enterica serovar Typhimurium
Ligand Molecules
Primary Citation
Structural and functional characterization of the nitrite channel NirC from Salmonella typhimurium.
Proc.Natl.Acad.Sci.USA 109 18395 18400 (2012)
PMID: 23090993 DOI: 10.1073/pnas.1210793109

Abstact

Nitrite (NO(2)(-)) is a central intermediate in the nitrogen metabolism of microorganisms and plants, and is used as a cytotoxin by macrophages as part of the innate immune response. The bacterial membrane protein NirC acts as a specific channel to facilitate the transport of nitrite anions across lipid bilayers for cytoplasmic detoxification. Despite NirC's importance in nitrogen metabolism and in the pathogenicity of enteric bacteria, available biochemical data are scarce. Here we present a functional and structural characterization of NirC from Salmonella typhimurium by lipid bilayer electrophysiology and X-ray crystallography. NirC is a pentameric member of the formate/nitrite transporter family of membrane proteins that operates as a channel with high conductance. Single-channel measurements reveal fast and slow gating events but, in contrast to the related FocA formate channel, no pH-dependent gating. A 2.4Å crystal structure of NirC at pH 5 shows similarity to FocA and aquaporins, but lacks the structural asymmetry observed in the formate channel at similarly low pH. Resolved water molecules in the protomers suggest a transport mechanism that also permits a facultative NO(2)(-)/H(+) symport.

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