Energetics of discrete selectivity bands and mutation-induced transitions in the calcium-sodium ion channels family
| Autor: | Kaufman, I., Luchinsky, D. G., Tindjong, R., McClintock, P. V. E., Eisenberg, R. S. |
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| Rok vydání: | 2013 |
| Předmět: | |
| Zdroj: | Phys. Rev. E 88, 052712 (2013) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevE.88.052712 |
| Popis: | We use Brownian dynamics simulations to study the permeation properties of a generic electrostatic model of a biological ion channel as a function of the fixed charge $Q_f$ at its selectivity filter. We reconcile the recently-discovered discrete calcium conduction bands M0 ($Q_f$=1e), M1 (3e), M2 (5e) with the set of sodium conduction bands L0 (0.5-0.7e), L1 (1.5-2e) thereby obtaining a completed pattern of conduction and selectivity bands v $Q_f$ for the sodium-calcium channels family. An increase of $Q_f$ leads to an increase of calcium selectivity: L0 (sodium selective, non-blocking channel) -> M0 (non-selective channel) -> L1 (sodium selective channel with divalent block) -> M1 (calcium selective channel exhibiting the anomalous mole fraction effect). We create a consistent identification scheme where the L0 band is identified with the eukaryotic (DEKA) sodium channel, and L1/L2 (speculatively) with the bacterial NaChBac channel. The scheme created is able to account for the experimentally observed mutation-induced transformations between non-selective channels, sodium-selective channels, and calcium-selective channels, which we interpret as transitions between different rows of the identification table. By considering the potential energy changes during permeation, we show explicitly that the multi-ion conduction bands of calcium and sodium channels arise as the result of resonant barrier-less conduction. Our results confirm the crucial influence of electrostatic interactions on conduction and on the Ca/Na valence selectivity of calcium and sodium ion channels. The model and results could be also applicable to biomimetic nanopores with charged walls. Comment: 16 pages, 17 figures, 2 tables, 75 references |
| Databáze: | arXiv |
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