FNT family ion channel

Experimental Data Snapshot

  • Resolution: 2.40 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.192 
  • R-Value Observed: 0.195 

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This is version 1.3 of the entry. See complete history


Structural and functional characterization of the nitrite channel NirC from Salmonella typhimurium.

Lu, W.Schwarzer, N.J.Du, J.Gerbig-Smentek, E.Andrade, S.L.Einsle, O.

(2012) Proc Natl Acad Sci U S A 109: 18395-18400

  • DOI: https://doi.org/10.1073/pnas.1210793109
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    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.

  • Organizational Affiliation

    Lehrstuhl für Biochemie, Institut für organische Chemie und Biochemie and BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Nitrite transporter NirC
A, B, C, D, E
A, B, C, D, E, F, G, H, I, J
261Salmonella enterica subsp. enterica serovar Typhimurium str. ST4/74Mutation(s): 0 
Gene Names: nirCSTM474_3643
Membrane Entity: Yes 
Find proteins for E8XEH9 (Salmonella typhimurium (strain 4/74))
Explore E8XEH9 
Go to UniProtKB:  E8XEH9
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupE8XEH9
Sequence Annotations
  • Reference Sequence
Small Molecules
Experimental Data & Validation

Experimental Data

  • Resolution: 2.40 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.192 
  • R-Value Observed: 0.195 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 176.3α = 90
b = 101.84β = 101.24
c = 205.3γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XPREPdata reduction

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-11-21
    Type: Initial release
  • Version 1.1: 2018-01-24
    Changes: Structure summary
  • Version 1.2: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Data collection, Database references, Derived calculations, Structure summary
  • Version 1.3: 2023-09-13
    Changes: Data collection, Database references, Refinement description, Structure summary