Department of Mathematics, Florida State University, Tallahassee, Florida 32306-4510, USA.
J Chem Phys. 2009 Dec 7;131(21):215101. doi: 10.1063/1.3268774.
The biophysical mechanisms underlying the relationship between the structure and function of the KcsA K(+) channel are described. Because of the conciseness of electrodiffusion theory and the computational advantages of a continuum approach, the Nernst-Planck (NP) type models, such as the Goldman-Hodgkin-Katz and Poisson-NP (PNP) models, have been used to describe currents in ion channels. However, the standard PNP (SPNP) model is known to be inapplicable to narrow ion channels because it cannot handle discrete ion properties. To overcome this weakness, the explicit resident ions NP (ERINP) model was formulated, which applies a local explicit model where the continuum model fails. Then, the effects of the ERI Coulomb potential, the ERI induced potential, and the ERI dielectric constant for ion conductance were tested in the ERINP model. The current-voltage (I-V) and current-concentration (I-C) relationships determined in the ERINP model provided biologically significant information that the traditional continuum model could not, explicitly taking into account the effects of resident ions inside the KcsA K(+) channel. In addition, a mathematical analysis of the K(+) ion dynamics established a tight structure-function system with a shallow well, a deep well, and two K(+) ions resident in the selectivity filter. Furthermore, the ERINP model not only reproduced the experimental results with a realistic set of parameters, but it also reduced CPU costs.
描述了 KcsA K(+)通道结构与功能关系的生物物理机制。由于电扩散理论的简洁性和连续体方法的计算优势，如 Goldman-Hodgkin-Katz 和 Poisson-NP (PNP) 模型，已被用于描述离子通道中的电流。然而，标准的 Poisson-NP (SPNP) 模型由于无法处理离散的离子特性，因此不适用于狭窄的离子通道。为了克服这一弱点，提出了显式驻留离子 Poisson-NP (ERINP) 模型，该模型在连续体模型失效的地方应用局部显式模型。然后，在 ERINP 模型中测试了 ERI 库仑势、ERI 诱导势和 ERI 介电常数对离子电导的影响。在 ERINP 模型中确定的电流-电压 (I-V) 和电流-浓度 (I-C) 关系提供了传统连续体模型无法提供的具有生物学意义的信息，明确考虑了 KcsA K(+)通道内驻留离子的影响。此外，对 K(+)离子动力学的数学分析建立了一个紧密的结构-功能系统，其中包括一个浅阱、一个深阱和两个驻留在选择性过滤器中的 K(+)离子。此外，ERINP 模型不仅用一组现实的参数重现了实验结果，而且还降低了 CPU 成本。
