试述通道和载体转运的异同点

发布网友发布时间：2022-05-26 19:03

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热心网友时间：2023-10-19 01:42

科罗拉多州立大学编写的《生物科学超文本》（Hypertexts for Biomedical Sciences）（http://www.vivo.colostate.e/hbooks/cmb/cells/pmemb/diffusion_f.html）中认为载体蛋白（carrier protein）和离子通道（ion channel，或所有通道蛋白）是易化扩散（协助运输）的两种主要承担者，而载体蛋白也可称为转运蛋白（transporter）。其中，“Carrier proteins bind a specific type of solute and are thereby inced to undergo a series of conformational changes which has the effect of carrying the solute to the other side of the membrane.”（载体蛋白能与某些特异的溶质结合并发生一系列形变使得结合的溶质转移到膜的另一侧）。

对于通道蛋白，其认为“Ion Channels do not really bind the solute, but are like hydrophilic pores through the membrane that open and allow certain types of solutes, usually inorganic ions, to pass through.”（离子通道并不与其转运的溶剂结合，而是让通常为无机离子的溶剂穿过）。《牛津生物化学词典》（Oxford Dictionary of Biochemistry）的解释是“An integral (cell membrane) protein that permits the controlled (gated) movement of ions through a membrane. ”（可以控制离跨膜运输的膜内在蛋白质）；《麦克格劳-希尔科技词典》（McGraw-Hill Science & Technology Dictionary）的解释是“Protein forming an aqueous pore spanning the lipid bilayer of the cell membrane which when open allows certain solutes to traverse the membrane.”（贯穿细胞膜磷脂双分子层的亲水蛋白质孔道，打开时允许某些特定溶质通过）。Answers.com给出的答案则比较完整、准确：“Channel proteins are integral proteins (also transmembrane proteins) which has pores that allow passage of water and hydrophilic solutes through the cell membrane.”（拥有孔道的、能允许水分子和亲水溶剂作跨膜运动的膜内在蛋白质）。

对于转运蛋白，维基百科中指出英文中较常用的“transporter”（转运体）是“transport protein”（转运蛋白）的简称，并明确说明“The proteins may assist in the movement of substances by facilitated diffusion or active transport.”（转运蛋白既能介导主动运输也能接介导易化扩散）。《神经科学》（Neuroscience (Purves D, Augustine GJ, Fitzpatrick D, et al.)）中对主动转运蛋白的的解释是“In contrast to the functions of ion channels, active transporters are membrane proteins that proce and maintain ion concentration gradients.”（与离子通道不同，转运蛋白主要用于产生并维持由离子浓度差异造成的膜电位），接着，其补充道“The most important of these is the Na+ pump, which hydrolyzes ATP to regulate the intracellular concentrations of both Na+ and K+. ”（最重要的例子是钠泵，该分子通过水解ATP来调节细胞内外钠离子与钾离子的浓度），这也从侧面印证了维基百科关于转运蛋白（亦即载体蛋白）可以参与主动运输（包括离子运输）的说法。