Ministry of Education Protein Science Laboratory, Center for Structural Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.
Nature. 2009 Nov 26;462(7272):467-72. doi: 10.1038/nature08610.
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.
FocA 是甲酸盐-亚硝酸盐转运体家族的代表性成员，该家族在细菌、古菌、真菌、藻类和寄生虫中转运短链酸。甲酸盐-亚硝酸盐转运体家族的结构和转运机制尚不清楚。在此，我们报告了大肠杆菌 FocA 的晶体结构，分辨率为 2.25Å。FocA 形成对称的五聚体，每个原体由六个跨膜片段组成。尽管缺乏序列同源性，但 FocA 原体的整体结构与水通道蛋白非常相似，强烈表明 FocA 是一种通道，而不是转运体。结构分析确定了潜在的重要通道残基，定义了通道路径，并揭示了两个紧缩位点。与水通道蛋白不同，FocA 不透水，但允许甲酸盐通过。结构和生化研究为 FocA 通道活性提供了机制上的见解。
