Abstract: FocA belongs to the formate-nitrate transporter (FNT) family and plays an essential role in the export and uptake of formate in organisms. According to the available crystal structures, the N-terminal residues of FocA are structurally featureless at physiological condition but form helices to harbor the cytoplasmic entrance of the substrate permeation pathway at reduced pH, which apparently explains the cease of electrical signal observed in the electrophysiological experiment. In this work, we found that those N-terminal helices cannot effectively preclude the substrate permeation by structural analysis and molecular dynamics simulations. Equilibrium simulations and thermodynamic calculations suggest that FocA is permeable to both formate and formic acid, the latter of which is transparent to electrophysiological studies as an electrically neutral species. Hence, the cease of electric current at acidic pH may be caused by the change of the transported substrate from formate to formic acid. In addition, the mechanism of formate export at physiological pH is also discussed.

 

报告人简介: 龚海鹏, 1997年和2000年在清华大学生物系分别获得学士和硕士学位, 2006年在Johns Hopkins University获得博士学位。之后, 分别在Johns Hopkins University和University of Chicago进行博士后研究。2009年回国, 加入清华大学生命学院。目前主要研究方向为: (1) 对重要膜蛋白的分子动力学模拟; (2) 蛋白质结构预测。