Beitz Eric, Becker Dana, von Bülow Julia, Conrad Christina, Fricke Nadine, Geadkaew Amornrat, Krenc Dawid, Song Jie, Wree Dorothea, Wu Binghua
Pharmaceutical Chemistry, University of Kiel, Gutenbergstrasse 76, Kiel, 24118, Germany.
Handb Exp Pharmacol. 2009(190):77-92. doi: 10.1007/978-3-540-79885-9_4.
Aquaporins enable the passage of a diverse set of solutes besides water. Many novel aquaporin permeants, such as antimonite and arsenite, silicon, ammonia, and hydrogen peroxide, have been described very recently. By the same token, the number of available aquaporin sequences has rapidly increased. Yet, sequence analyses and structure models cannot reliably predict permeability properties. Even the contribution to pore selectivity of individual residues in the channel layout is not fully understood. Here, we describe and discuss established in vitro assays for water and solute permeability. Measurements of volume change due to flux along osmotic or chemical gradients yield quantitative biophysical data, whereas phenotypic growth assays can hint at the relevance of aquaporins in the physiological setting of a certain cell. We also summarize data on the modification of pore selectivity of the prototypical water-specific mammalian aquaporin-1. We show that replacing residues in the pore constriction region allows ammonia, urea, glycerol, and even protons to pass the aquaporin pore.
水通道蛋白除了能让水通过外，还能使多种溶质通过。最近已经描述了许多新型的水通道蛋白渗透物，如亚锑酸盐和亚砷酸盐、硅、氨和过氧化氢。同样，可用的水通道蛋白序列数量也迅速增加。然而，序列分析和结构模型无法可靠地预测通透性特性。甚至对于通道布局中单个残基对孔选择性的贡献也尚未完全了解。在这里，我们描述并讨论已确立的水和溶质通透性的体外测定方法。测量由于沿渗透或化学梯度的通量引起的体积变化可产生定量的生物物理数据，而表型生长测定可以提示水通道蛋白在特定细胞生理环境中的相关性。我们还总结了关于典型的水特异性哺乳动物水通道蛋白-1孔选择性修饰的数据。我们表明，替换孔收缩区域中的残基可使氨、尿素、甘油甚至质子通过水通道蛋白孔。
