Krofchick Daniel, Silverman Mel
Institute of Biomaterials and Biomedical Engineering and Canadian Institutes for Health Research Group in Membrane Biology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
Biophys J. 2003 Jun;84(6):3690-702. doi: 10.1016/S0006-3495(03)75098-X.
The Na(+) and voltage-dependence of transient rabbit Na(+)/glucose cotransporter (rSGLT1) kinetics was studied with the two-electrode voltage-clamp technique and Xenopus laevis oocytes. Using step changes in membrane potential, in the absence of glucose but with 100 or 10 mM Na(+), transient currents were measured corresponding to binding/debinding of Na(+) and conformational changes of the protein. Previously, only a single time constant has been published for rSGLT1. We, however, observed three decay components; a fast (tau(f), 0.5-1 ms) voltage- and Na(+)-independent decay, and medium (tau(m), 0.5-4 ms) and slow (tau(s), 8-50 ms) voltage- and Na(+)-dependent decays. Transient currents were simulated and fit using a four-state model to obtain kinetic parameters for the system. The four-state model was able to reconstitute an assortment of experimental data.
采用双电极电压钳技术并利用非洲爪蟾卵母细胞，研究了瞬时兔钠/葡萄糖共转运体（rSGLT1）动力学的钠（Na⁺）依赖性和电压依赖性。在不存在葡萄糖但含有100 mM或10 mM Na⁺的情况下，通过膜电位的阶跃变化，测量了与Na⁺的结合/解离以及蛋白质构象变化相对应的瞬时电流。此前，关于rSGLT1仅公布了一个时间常数。然而，我们观察到了三个衰减成分：一个快速的（τ(f)，0.5 - 1毫秒）与电压和Na⁺无关的衰减，以及中等的（τ(m)，0.5 - 4毫秒）和缓慢的（τ(s)，8 - 50毫秒）与电压和Na⁺有关的衰减。使用四态模型对瞬时电流进行模拟和拟合，以获得该系统的动力学参数。四态模型能够重构各种实验数据。
