|Title||Structure of the formate transporter FocA reveals a pentameric aquaporin-like channel.|
|Publication Type||Journal Article|
|Year of Publication||2009|
|Authors||Wang, Y, Huang, Y, Wang, J, Cheng, C, Huang, W, Lu, P, Xu, Y-N, Wang, P, Yan, N, Shi, Y|
|Date Published||2009 Nov 26|
|Keywords||Aquaporins, Crystallography, X-Ray, Escherichia coli, Escherichia coli Proteins, Formates, Liposomes, Membrane Transport Proteins, Models, Molecular, Molecular Mimicry, Mutation, Permeability, Protein Structure, Quaternary, Structure-Activity Relationship, Water|
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.