Gadsby David C
Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, 1230 York Avenue, New York, New York 10065-6399, USA.
Nat Rev Mol Cell Biol. 2009 May;10(5):344-52. doi: 10.1038/nrm2668. Epub 2009 Apr 2.
The incessant traffic of ions across cell membranes is controlled by two kinds of border guards: ion channels and ion pumps. Open channels let selected ions diffuse rapidly down electrical and concentration gradients, whereas ion pumps labour tirelessly to maintain the gradients by consuming energy to slowly move ions thermodynamically uphill. Because of the diametrically opposed tasks and the divergent speeds of channels and pumps, they have traditionally been viewed as completely different entities, as alike as chalk and cheese. But new structural and mechanistic information about both of these classes of molecular machines challenges this comfortable separation and forces its re-evaluation.
离子持续不断地穿过细胞膜，这一过程由两类“边界守卫”控制：离子通道和离子泵。开放的通道允许特定离子顺着电势梯度和浓度梯度快速扩散，而离子泵则不知疲倦地工作，通过消耗能量将离子进行热力学逆梯度缓慢转运，从而维持这些梯度。由于通道和泵的任务截然相反，且速度差异很大，传统上它们被视为完全不同的实体，就像粉笔和奶酪一样毫无相似之处。但是，关于这两类分子机器的新结构和机制信息对这种简单的区分提出了挑战，促使人们重新审视这一观点。
