Wang Y, Huang YJ, Wang JW, Cheng C, Huang WJ, Lu PL, Xu YN, Wang PY, Yan N, Shi YG. Structure of the formate transporter FocA reveals a pentameric aquaporin-like channel. NATURE 462: 467-472, 2009

Abstract 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......