Transport of water and glycerol in aquaporin 3 is gated by H+
Transport of water and glycerol in aquaporin 3 is gated by H+
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DOI：
10.1074/jbc.274.31.21631
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发表时间：
1999-07-30
影响因子：
4.8
通讯作者：
Klaerke, DA
中科院分区：
文献类型：
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作者：
Zeuthen, T;Klaerke, DA
为了研究外界pH和溶质结构对卵母细胞水通道蛋白（AQP）通透性的影响，在非洲爪蟾卵母细胞中表达AQP。对于AQP3的渗透水渗透性，L-p，被废除在酸性pH值与pK为6.4和希尔系数为3。AQP0、AQP1、AQP2、AQP4和AQP5的L-p值与pH无关。对于AQP3，从[C-14]甘油摄取获得的甘油渗透性P-G1在pK为6.1和Hill系数为6的酸性pH值下被消除。因此，AQP3在生理pH下充当甘油和水通道，但在pH值约6.1时主要充当甘油通道。pH值的影响是可逆的。水和直链多元醇的通量之间的相互作用从反射系数推断）。对于AQP3，水和甘油通过竞争可滴定位点而相互作用：σ（GI）在中性pH下为0.15，但在pH 6.4下加倍。其中-OH基团自由形成氢键的多元醇的σ值较小。输运过程的活化能约为5 kcal mol（-1）。我们认为，水和多元醇渗透AQP3形成连续的氢键与滴定网站。
Aquaporins (AQPs) were expressed in Xenopus laevis oocytes in order to study the effects of external pH and solute structure on permeabilities. For AQP3 the osmotic water permeability, L-p, was abolished at acid pH values with a pK of 6.4 and a Hill coefficient of 3. The L-p values of AQP0, AQP1, AQP2, AQP4, and AQP5 were independent of pH, For AQP3 the glycerol permeability P-Gl, obtained from [C-14]glycerol uptake, was abolished at acid pH values with a pK of 6.1 and a Hill coefficient of 6. Consequently, AQP3 acts as a glycerol and water channel at physiological pH, but predominantly as a glycerol channel at pH values around 6.1. The pH effects were reversible. The interactions between fluxes of water and straight chain polyols were inferred from reflection coefficients to). For AQP3, water and glycerol interacted by competing for titratable site(s): sigma(Gl) was 0.15 at neutral pH but doubled at pH 6.4. The sigma values were smaller for polyols in which the -OH groups were free to form hydrogen bonds. The activation energy for the transport processes was around 5 kcal mol(-1). We suggest that water and polyols permeate AQP3 by forming successive hydrogen bonds with titratable sites.