MECHANISM OF ION PERMEATION THROUGH CALCIUM CHANNELS
MECHANISM OF ION PERMEATION THROUGH CALCIUM CHANNELS
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DOI：
10.1038/309453a0
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发表时间：
1984-01-01
期刊：
影响因子：
64.8
通讯作者：
TSIEN, RW
中科院分区：
文献类型：
--
作者：
HESS, P;TSIEN, RW
Calcium channels carry out vital functions in a wide variety of excitable cells1–4but they also face special challenges. In the medium outside the channel, Ca2+ions are vastly outnumbered by other ions. Thus, the calcium channel must be extremely selective if it is to allow Ca2+influx rather than a general cation influx. In fact, calcium channels show a much greater selectivity for Ca2+than sodium channels do for Na+(refs 5–9) despite the high flux that open Ca channels can support3–4. Relatively little is known about the mechanism of ion permeation through Ca channels. Earlier models assumed ion independence5or single-ion occupancy10–16. Here we present evidence for a novel hypothesis of ion movement through Ca channels, based on measurements of Ca channel activity at the level of single cells or single channels. Our results indicate that under physiological conditions, the channel is occupied almost continually by one or more Ca2+ions which, by electrostatic repulsion, guard the channel against permeation by other ions. On the other hand, repulsion between Ca2+ions allows high throughput rates and tends to prevent saturation with calcium.
