Ganea Constanta, Fendler Klaus
Biophysical Department, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania.
Biochim Biophys Acta. 2009 Jun;1787(6):706-13. doi: 10.1016/j.bbabio.2009.02.002. Epub 2009 Feb 11.
A comparative review of the electrophysiological characterization of selected secondary active transporters from Escherichia coli is presented. In melibiose permease MelB and the Na(+)/proline carrier PutP pre-steady-state charge displacements can be assigned to an electrogenic conformational transition associated with the substrate release process. In both transporters cytoplasmic release of the sugar or the amino acid as well as release of the coupling cation are associated with a charge displacement. This suggests a common transport mechanism for both transporters. In the NhaA Na(+)/H(+) exchanger charge translocation due to its steady-state transport activity is observed. A new model is proposed for pH regulation of NhaA that is based on coupled Na(+) and H(+) equilibrium binding.
本文对来自大肠杆菌的选定次级主动转运蛋白的电生理特性进行了比较综述。在蜜二糖通透酶MelB和Na(+)/脯氨酸载体PutP中，稳态前电荷位移可归因于与底物释放过程相关的电生构象转变。在这两种转运蛋白中，糖或氨基酸的胞质释放以及偶联阳离子的释放都与电荷位移相关。这表明这两种转运蛋白具有共同的转运机制。在NhaA Na(+)/H(+)交换器中，观察到由于其稳态转运活性而导致的电荷转运。基于耦合的Na(+)和H(+)平衡结合，提出了一种新的NhaA pH调节模型。
