4FC4

FNT family ion channel

Summary for 4FC4

• Entry DOI: 10.2210/pdb4fc4/pdb
• Related: 3Q7K
• Descriptor: Nitrite transporter NirC, octyl beta-D-glucopyranoside (3 entities in total)
• Functional Keywords: alpha-helical inner membrane protein, ion channel, cytoplasmic membrane, transport protein
• Biological source: Salmonella enterica subsp. enterica serovar Typhimurium
• Total number of polymer chains: 10
• Total formula weight: 281382.53

Authors

Lue, W.,Schwarzer, N.,Du, J.,Gerbig-Smentek, E.,Andrade, S.L.A.,Einsle, O. (deposition date: 2012-05-24, release date: 2012-11-21, Last modification date: 2023-09-13)

Primary citation

Lu, W.,Schwarzer, N.J.,Du, J.,Gerbig-Smentek, E.,Andrade, S.L.,Einsle, O.
Structural and functional characterization of the nitrite channel NirC from Salmonella typhimurium.
Proc.Natl.Acad.Sci.USA, 109:18395-18400, 2012

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.

PubMed: 23090993
DOI: 10.1073/pnas.1210793109

Experimental method

X-RAY DIFFRACTION (2.4 Å)