Abstract
Aquaporins (AQPs) constitute an ancient and diverse protein family present in all living organisms, indicating a common ancient ancestor. However, during evolution, these organisms appear and evolve differently, leading to different cell organizations and physiological processes. Amongst the eukaryotes, an important distinction between plants and animals is evident, the most conspicuous difference being that plants are sessile organisms facing ever-changing environmental conditions. In addition, plants are mostly autotrophic, being able to synthesize carbohydrates molecules from the carbon dioxide in the air during the process of photosynthesis, using sunlight as an energy source. It is therefore interesting to analyze how, in these different contexts specific to both kingdoms of life, AQP function and regulation evolved. This review aims at highlighting similarities and differences between plant and mammal AQPs. Emphasis is given to the comparison of isoform numbers, their substrate selectivity, the regulation of the subcellular localization, and the channel activity.
Highlights
Membrane intrinsic proteins (MIPs), ambiguously named aquaporins (AQPs), are channel proteins facilitating the passive movement of water and an increasing list of small solutes across biological membranes
Animal MIPs are usually classified into four groups: the classical or orthodox AQPs (AQP0, 1, 2, 4, 5, 6, 14) that are associated with water transport, the aqua-ammoniaporins (AQP8) sometimes included in the orthodox AQPs, the aquaglyceroporins (AQP3, 7, 9, 10, 13), and the unorthodox AQPs (AQP11–12) [6,7,8,9]
Some interesting differences between plant and mammal AQPs come from comparison of the post-translational regulation processes
Summary
Membrane intrinsic proteins (MIPs), ambiguously named aquaporins (AQPs), are channel proteins facilitating the passive movement of water and an increasing list of small solutes across biological membranes. A pair of NPA (Asn-Pro-Ala) motifs held by the diving short helices constitutes the first filter region. They position entering molecules correctly by forming hydrogen bonds and establishing an electrostatic repulsion of cations and protons [4,5]. The tetrameric structure suggests the presence of a fifth pore in its center, whose presence and role in solute transport is still a matter of debate. Despite those shared structural features, the MIP family is a large and diversified protein family at the sequence and functional levels. Plants express a much greater number of MIPs that were probably conserved due to the functional advantages linked to the plant lifestyle
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