Structure of the formate transporter FocA reveals a pentameric aquaporin-like channel.
FocA is a representative member of the formate-nitrite transporter family, which transports short-chain acids in bacteria, archaea, fungi, algae and parasites. The structure and transport mechanism of the formate-nitrite transporter family remain unknown. Here we report the crystal structure of Escherichia coli FocA at 2.25 A resolution. FocA forms a symmetric pentamer, with each protomer consisting of six transmembrane segments. Despite a lack of sequence homology, the overall structure of the FocA protomer closely resembles that of aquaporin and strongly argues that FocA is a channel, rather than a transporter. Structural analysis identifies potentially important channel residues, defines the channel path and reveals two constriction sites. Unlike aquaporin, FocA is impermeable to water but allows the passage of formate. A structural and biochemical investigation provides mechanistic insights into the channel activity of FocA.
Wang
Yi
Y
Ministry of Education Protein Science Laboratory, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.
Huang
Yongjian
Y
Wang
Jiawei
J
Cheng
Chao
C
Huang
Weijiao
W
Lu
Peilong
P
Xu
Ya-Nan
YN
Wang
Pengye
P
Yan
Nieng
N
Shi
Yigong
Y
D020346:Aquaporins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005561:Formates / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D018716:Molecular Mimicry; D009154:Mutation; D010539:Permeability; D020836:Protein Structure, Quaternary; D013329:Structure-Activity Relationship; D014867:Water / Q000032:analysis / Q000378:metabolism
D020346:Aquaporins; D029968:Escherichia coli Proteins; C088103:FocA protein, E coli; D005561:Formates; D008081:Liposomes; D026901:Membrane Transport Proteins; D014867:Water; C030544:formic acid