Water channel proteins, classified as a family of Membrane Intrinsic Proteins (MIPs) superfamily, enable rapid movement of water and small uncharged molecules through biological membranes. Although water channel proteins are required in several important processes characteristic for the animals, such as osmoregulation, mucus secretion, or defense against desiccation, molluscs, until now, have been very poorly explored in this aspect. Therefore, we decided to study MIPs in Helix pomatia L. applied as a model in studies on terrestrial snail physiology. Our studies consisted in: the snail organ transcriptome sequencing and consecutive bioinformatic analysis of the predicted protein, estimation of the encoding transcript expression (qPCR), investigation of the predicted protein function in the yeast Saccharomyces cerevisiae cells, and the phylogenetic analysis. We identified six water channel proteins, named HpAQP1 to HpAQP6. All of them were proven to transport water, two of them (HpAQP3 and HpAQP4) were also shown to be able to transport glycerol, and other two (HpAQP5 and HpAQP6) to transport H2O2. Phylogenetic analysis indicated that the proteins either fell into aquaporins (HpAQP1, HpAQP2 and HpAQP5) or formed new groups of invertebrate water channel proteins, not described until now, that we suggest to term malacoglyceroporins (HpAQP3 and HpAQP4) and malacoaquaporins (HpAQP6). Thus, the classification of animal water channels based on the vertebrate proteins and including aquaporin, aquaglyceroporin, S-aquaporin and AQP8-type grades does not reflect diversity of these proteins in invertebrates. The obtained results provide important data concerning diversity of water channel protein repertoire in aquatic and terrestrial invertebrates and should also contribute to the improvement of animal water channel classification system.

中文翻译：

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基于蜗牛螺旋线虫（Helicidae）MIP蛋白的鉴定和系统发育分析，推定了新的无脊椎动物水通道组。

水通道蛋白被归类为膜内在蛋白（MIPs）超家族，可以使水和不带电荷的小分子快速移动通过生物膜。尽管水通道蛋白在动物的几个重要特征过程中是必需的，例如渗透压调节，粘液分泌或抗干燥作用，但是直到现在，在这方面对软体动物的研究还很少。因此，我们决定研究螺旋螺旋藻中的MIPs，作为陆生蜗牛生理学研究的模型。我们的研究包括：蜗牛器官转录组测序和预测蛋白质的连续生物信息学分析，编码转录本表达（qPCR）的估计，酵母酿酒酵母细胞中预测蛋白质功能的研究，以及系统发育分析。我们确定了六个水通道蛋白，名为HpAQP1至HpAQP6。事实证明，它们全部都能运输水，其中两个（HpAQP3和HpAQP4）也能够运输甘油，另外两个（HpAQP5和HpAQP6）能够运输H2O2。系统发育分析表明，这些蛋白要么落入水通道蛋白（HpAQP1，HpAQP2和HpAQP5）中，要么形成了新的无脊椎动物水通道蛋白组，直到现在为止仍未描述，因此我们建议使用malacoglyceroporins（HpAQP3和HpAQP4）和malacoaquaporins（HpAQP6）。因此，基于脊椎动物蛋白并包括水通道蛋白，水甘油通道蛋白，S-水通道蛋白和AQP8型等级的动物水通道的分类不能反映这些蛋白在无脊椎动物中的多样性。