Theoretical Biology and Biophysics Group and Center for Nonlinear Studies, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America.
PLoS Comput Biol. 2010 Jun 10;6(6):e1000804. doi: 10.1371/journal.pcbi.1000804.
The functioning of living cells requires efficient and selective transport of materials into and out of the cell, and between different cellular compartments. Much of this transport occurs through nano-scale channels that do not require large scale molecular re-arrangements (such as transition from a 'closed' to an 'open' state) and do not require a direct input of metabolic energy during transport. Nevertheless, these 'always open' channels are highly selective and pass only their cognate molecules, while efficiently excluding all others; indeed, these channels can efficiently transport specific molecules even in the presence of a vast excess of non-specific molecules. Such biological transporters have inspired the creation of artificial nano-channels. These channels can be used as nano-molecular sorters, and can also serve as testbeds for examining modes of biological transport. In this paper, we propose a simple kinetic mechanism that explains how the selectivity of such 'always open' channels can be based on the exclusion of non-specific molecules by specific ones, due to the competition for limited space inside the channel. The predictions of the theory account for the behavior of the nuclear pore complex and of artificial nanopores that mimic its function. This theory provides the basis for future work aimed at understanding the selectivity of various biological transport phenomena.
活细胞的功能需要有效地将物质选择性地输入和输出细胞，并在不同的细胞隔室之间进行运输。这种运输的大部分是通过纳米级通道进行的，这些通道不需要大规模的分子重新排列（例如从“关闭”状态到“打开”状态），并且在运输过程中不需要直接输入代谢能量。然而，这些“始终打开”的通道具有高度的选择性，只允许其同源分子通过，同时有效地排除所有其他分子；事实上，这些通道甚至可以在存在大量非特异性分子的情况下有效地运输特定的分子。这些生物转运蛋白激发了人工纳米通道的创造。这些通道可用作纳米分子分拣器，也可用作研究生物转运模式的试验台。在本文中，我们提出了一种简单的动力学机制，该机制解释了由于对通道内有限空间的竞争，这种“始终打开”的通道的选择性如何基于对非特异性分子的排除来实现特异性分子的选择性。该理论的预测解释了核孔复合体和模拟其功能的人工纳米孔的行为。该理论为未来旨在理解各种生物转运现象的选择性的工作提供了基础。
