变构调节
共转运蛋白
化学计量学
高氯酸盐
化学
膜转运
生物物理学
生物化学
运输机
膜
离子
基因
生物
酶
物理化学
有机化学
作者
Alejandro Llorente-Esteban,Rían W. Manville,Andrea Reyna-Neyra,Geoffrey W. Abbott,L.M. Amzel,Nancy Carrasco
标识
DOI:10.1038/s41594-020-0417-5
摘要
The Na+/I- symporter (NIS), the plasma membrane protein that actively transports I- (stoichiometry 2Na+:1I-) in thyroid physiology and radioiodide-based thyroid cancer treatment, also transports the environmental pollutant perchlorate (stoichiometry 1Na+:1ClO4-), which competes with I- for transport. Until now, the mechanism by which NIS transports different anion substrates with different stoichiometries has remained unelucidated. We carried out transport measurements and analyzed these using a statistical thermodynamics-based equation and electrophysiological experiments to show that the different stoichiometry of ClO4- transport is due to ClO4- binding to a high-affinity non-transport allosteric site that prevents Na+ from binding to one of its two sites. Furthermore, low concentrations of ClO4- inhibit I- transport not only by competition but also, critically, by changing the stoichiometry of I- transport to 1:1, which greatly reduces the driving force. The data reveal that ClO4- pollution in drinking water is more dangerous than previously thought.
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