Research On Permeability Of NaK Channel

The process of ion transmembrane transportation is the transfer process of the material, energy and the information systematically, which is one of the research focus of biology. The structure of membrane protein determines the function of ion transportation and plays a key role in the process of the transportation. The research will contribute to our more thorough and more meticulous comprehension of a life process of material acrossing membrane and is helpful for us to refine some new physical problems which may enrich the theory of transportation.Based on the three-dimensional high-resolution structure of NaK channel, which is reported by Ning Shi in 2006 for the first time, the paper adopts the quantum chemistry and density functional theory to construct the potential curves reflecting the interaction energy of the channel with sodium ion, potassium ion and rubidium ion on the molecule level respectively. Then the Brownian dynamics model is built to simulate the transport process of the ions. At last, the structures and permeabilities of NaK channel and KcsA potassium channel are compared and the essential relation between the structure of channel and the function of channel is analyzed. some useful conclusions are gotten:(1) The potential curves reflecting the interaction energy of NaK channel with sodium ion, potassium ion and rubidium ion are all dissymmetry, which can make the monovalent cation pass through the channel from the intracellular side to the extracellular side. It indicates that the channel loses its selectivity to different monovalent cation.(2) These minimum points of the potential curves are corresponding to the ion binding sites in the selectivity filter of the NaK channel. Sodium ion, potassium ion and rubidium ion all have their binding sites, which are consistent with the experimental data.(3) For sodium ion, potassium ion and rubidium ion, the average velocity, the permeable time of a single ion, and permeable rate are obtained. The results are consistent with the experimental results. the dynamics characteristic shows that the permeant process has the"most suitable radius".This work is supported by the National Natural Science Foundation of China (10775038, 10645006, 10647121), the Specialized Research Fund for the Doctoral Program of Higher Education of China ( 20060080001 ) the Hebei Provincial Natural Science Foundation (C2005000011,C2007000026) , and the Foundation of Education Bureau of Hebei Province(2006148).