THE VACUOLAR MEMBRANE-PROTEIN GAMMA-TIP CREATES WATER SPECIFIC CHANNELS IN XENOPUS-OOCYTES
THE VACUOLAR MEMBRANE-PROTEIN GAMMA-TIP CREATES WATER SPECIFIC CHANNELS IN XENOPUS-OOCYTES
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DOI：
10.1002/j.1460-2075.1993.tb05877.x
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发表时间：
1993-06-01
期刊：
影响因子：
11.4
通讯作者：
CHRISPEELS, MJ
中科院分区：
文献类型：
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作者：
MAUREL, C;REIZER, J;CHRISPEELS, MJ
高等植物细胞的液泡膜（液泡膜）含有丰富的27 kDa蛋白质，称为TIP（液泡膜内在蛋白），其以不同的同种型存在，并且属于在细菌、植物和动物中发现的同源通道样蛋白的大家族。在本研究中，我们确定和功能的γ-TIP从拟南芥的蛋白表达在非洲爪蟾卵母细胞。γ-TIP使卵母细胞的渗透水渗透性增加6- 8倍，达到1-1.5 × 10 - 2 cm/s。最近被鉴定为红细胞水通道的同源人红细胞蛋白质CHIP 28也得到了类似的结果。细菌同系物GlpF不影响卵母细胞的渗透水渗透性，但有利于甘油的摄取，根据其已知的功能。相比之下，γ-TIP没有促进甘油渗透性。电压钳实验提供的证据表明，γ-TIP诱导卵母细胞中没有产电离子运输，特别是在渗透压挑战，导致大量的水运输。这些结果使我们能够得出结论，MIP家族的各种蛋白质成员具有独特和特异性的运输功能，植物蛋白γ-TIP可能作为液泡膜中的水特异性通道发挥作用。
The vacuolar membrane (tonoplast) of higher plant cells contains an abundant 27 kDa protein called TIP (tonoplast intrinsic protein) that occurs in different isoforms and belongs to a large family of homologous channel-like proteins found in bacteria, plants and animals. In the present study, we identified and characterized the function of gamma-TIP from Arabidopsis thaliana by expression of the protein in Xenopus oocytes. gamma-TIP increased the osmotic water permeability of oocytes 6- to 8-fold, to values in the range 1-1.5 x 10(-2) cm/s. Similar results were obtained with the homologous human erythrocyte protein CHIP28, recently identified as the erythrocyte water channel. The bacterial homolog GlpF did not affect the osmotic water permeability of oocytes, but facilitated glycerol uptake, in accordance with its known function. By contrast, gamma-TIP did not promote glycerol permeability. Voltage clamp experiments provided evidence showing that gamma-TIP induced no electrogenic ion transport in oocytes, especially during osmotic challenge that resulted in massive transport of water. These results allow us to conclude that the various protein members of the MIP family have unique and specific transport functions and that the plant protein gamma-TIP likely functions as a water specific channel in the vacuolar membrane.