LEAF, Linking Landscape, Environment, Agriculture and Food, and DRAT, Dept. de Recursos Biológicos, Ambiente e Território, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, 1649-003 Lisboa, Portugal.
Int J Mol Sci. 2020 Jan 19;21(2):663. doi: 10.3390/ijms21020663.
Plant Nodulin 26-like Intrinsic Proteins (NIPs) are multifunctional membrane channels of the Major Intrinsic Protein (MIP) family. Unlike other homologs, they have low intrinsic water permeability. NIPs possess diverse substrate selectivity, ranging from water to glycerol and to other small solutes, depending on the group-specific amino acid composition at aromatic/Arg (ar/R) constriction. We cloned three (, and ) from grapevine (cv. Touriga Nacional). Their expression in the membrane of enabled their functional characterization for water and glycerol transport through stopped-flow spectroscopy. TnNIP1;1 demonstrated high water as well as glycerol permeability, whereas TnNIP6;1 was impermeable to water but presented high glycerol permeability. Their transport activities were declined by cytosolic acidification, implying that internal-pH can regulate NIPs gating. Furthermore, an extension of C-terminal in TnNIP6;1M homolog, led to improved channel activity, suggesting that NIPs gating is putatively regulated by C-terminal. Yeast growth assays in the presence of diverse substrates suggest that the transmembrane flux of metalloids (As, B, and Se) and the heavy metal (Cd) are facilitated through grapevine NIPs. This is the first molecular and functional characterization of grapevine NIPs, providing crucial insights into understanding their role for uptake and translocation of small solutes, and extrusion of toxic compounds in grapevine.
植物类通道蛋白 26 样内在蛋白（NIPs）是水通道蛋白（MIP）家族的多功能膜通道。与其他同源物不同，它们的内在水透性较低。NIPs 具有不同的底物选择性，范围从水到甘油和其他小溶质，这取决于芳香族/精氨酸（ar/R）收缩处特定组氨基酸组成。我们从葡萄（cv. Touriga Nacional）中克隆了三个（ 、 和 ）。在 的膜中表达它们，通过停流光谱法对其水和甘油运输功能进行了表征。TnNIP1;1 表现出高水和甘油通透性，而 TnNIP6;1 对水不可渗透，但表现出高甘油通透性。它们的转运活性受到胞质酸化的抑制，这表明内部 pH 可以调节 NIPs 的门控。此外，在 TnNIP6;1M 同源物的 C 末端延长，导致通道活性提高，这表明 NIPs 的门控可能受到 C 末端的调节。在存在多种底物的酵母生长测定中，表明金属（As、B 和 Se）和重金属（Cd）的跨膜通量是通过葡萄 NIPs 促进的。这是对葡萄 NIPs 的首次分子和功能表征，为了解它们在葡萄中吸收和转运小分子以及排出有毒化合物的作用提供了重要的见解。
