Fisahn J, Hansen U P, Lucas W J
Department of Botany, University of California, Davis 95616.
Proc Natl Acad Sci U S A. 1992 Apr 15;89(8):3261-5. doi: 10.1073/pnas.89.8.3261.
Biophysical and numerical analysis methods were used to characterize and model the transport protein that gives rise to the acid and alkaline regions of Chara. A measuring system that permits the detection of area-specific current-voltage curves was used. These current-voltage curves, obtained from the inward current regions of Chara, underwent a parallel shift when the alkaline region was inverted by means of an acid pH treatment. In this situation the reversal potential of this area shifted from -120 mV to -340 mV. Together with data obtained from experiments using a divided chamber system, these results suggest that a common transport protein generates inward and outward current regions of Chara. On the basis of these experimental findings, a reaction kinetic model is proposed that assigns two operational modes to the proposed transport protein. Switching between these modes generates either acid or alkaline behavior. Since the observed pH dependence of the postulated transporter is rather complex, a reaction kinetic saturation mechanism had to be incorporated into the model. This final 10-state reaction kinetic model provides an appropriate set of mathematical relations to fit the measured current-voltage curves by computer.
采用生物物理和数值分析方法对导致轮藻酸性和碱性区域的转运蛋白进行表征和建模。使用了一种能够检测区域特异性电流-电压曲线的测量系统。这些从轮藻内向电流区域获得的电流-电压曲线，在通过酸性pH处理使碱性区域反转时发生了平行移动。在这种情况下，该区域的反转电位从-120 mV 变为-340 mV。结合使用分隔室系统的实验获得的数据，这些结果表明，一种共同的转运蛋白产生了轮藻的内向和外向电流区域。基于这些实验结果，提出了一个反应动力学模型，该模型为所提出的转运蛋白赋予了两种操作模式。在这些模式之间切换会产生酸性或碱性行为。由于观察到的假定转运体对pH的依赖性相当复杂，因此必须将反应动力学饱和机制纳入模型。这个最终的十态反应动力学模型提供了一组合适的数学关系，以便通过计算机拟合测量的电流-电压曲线。
