Sixteen years have passed since human aquaporin-1 (AQP1) was discovered as the first water channel, facilitating trans-membrane water fluxes. Subsequent years of research showed that the water channel AQP1 was only the tip of an iceberg; the iceberg itself being the ubiquitous super family of membrane intrinsic proteins (MIPs) that facilitate trans-membrane transport of water and an increasing number of small, water-soluble and uncharged compounds. Here we introduce you to the superfamily of MIPs and provide a summary about our gradually refined understanding of the phylogenetic relationship of its members. This volume is dedicated to the metalloids, a recently discovered group of substrates for a number of specific MIPs in a diverse spectrum of organisms. Particular focus is given to the essential boron, the beneficial silicon and the highly toxic arsenic. The respective MIP isoforms that facilitate the transport of these metalloids include members from several clades of the phylogenetic tree, suggesting that metalloid transport is an ancient function within this family of channel proteins. Among all the various substrates that have been shown to be transported by MIPs, metalloids take an outstanding position. While water transport seems to be a common function of many MIPs, single isoforms in plants have been identified as being crucially important for the uptake of boric acid as well as silicic acid. Here, the function seems not to be redundant, as mutations in those genes render plants deficient in boron and silicon, respectively.

Dedicated to the metalloids, a recently discovered group of substrates for a number of specific MIPs in a diverse spectrum of organisms

1. Aquaporins: A Family of Highly Regulate d Multifunctional ChannelsCharles Hachez and François ChaumontAbstractIntroduction¿The Discovery of AquaporinsTopology of AquaporinsSelectivity of AquaporinsMeasurement of Aquaporin Activity and Water MovementAquaporin InhibitionPhenotype Analysis Reveals Involvement of Aquaporins in Key Physiological ProcessesAquaporin Regulation: Gating and LocalizationConclusion2. Phylogeny of Major Intrinsic ProteinsJonas Å.H. Danielson and Urban JohansonAbstractIntroductionA Historical Account of the MIP PhylogenyPlant MIPsPhylogenetic Analysis of NIPsSolute TransportNIP?Like Bacterial MIPs and Ancestral State of ar/R FilterConclusion3. Metalloids, Soil Chemistry and the EnvironmentEnzo Lombi and Peter E. HolmAbstractIntroductionHistorical PerspectiveEnvironmental RelevanceFactors Controlling BioavailabilityAssessing Soil Bioavailability of MetalloidsConclusion4. Arsenic Transport in Prokaryotes and Eukaryotic MicrobesBarry P. Rosen and Markus J. TamásAbstractIntroductionMetalloid Transport in ProkaryotesMetalloid Transport in Eukaryotic MicrobesConclusion5. Metalloid Transport by Aquaglyceroporins: Consequences in the Treatment of Human DiseasesRita Mukhopadhyay and Eric BeitzAbstractIntroductionMetalloids and CancerUptake of Metalloids via Human AquaglyceroporinsMetalloids in Protozoan Parasitic InfectionsParasite Aquaglyceroporins Facilitate Metalloid TransportTherapeutic Modulation of AQP PermeabilityConclusion6. Roles of Vertebrate Aquaglyceroporins in Arsenic Transport and DetoxificationZijuan LiuAbstractIntroductionExpression of Vertebrate AquaglyceroporinsArsenic Is Both an Environmental Toxin and Human CarcinogenUptake of Organic and Inorganic Arsenic via AquaglyceroporinsMolecular Mechanisms for Arsenic Translocation by AquaglyceroporinsArsenic Toxicity in Relation of Aquaglyceroporins RegulationPerspectivesConclusion7. Molecular Mechanisms of Boron Transportin Plants: Involvement of Arabidopsis NIP5;1 and NIP6;1Kyoko Miwa, Mayuki Tanaka, Takehiro Kamiya and Toru FujiwaraAbstractPhysiological Function of Boron in PlantsPhysiological Analysis of B TransportMolecular Mechanisms of B TransportImprovement of Plant Growth Property through BOR and NIP TransportersConclusion and Foresights8. Silicon Transporters in Higher PlantsJian Feng MaAbstractIntroductionSilicon TransportersInflux Si TransportersEfflux Transporter of SiliconDifference in Si Uptake System between Paddy and Field CropsSilicon Transporters for Xylem UnloadingConclusion9. Major Intrinsic Proteins and Arsenic Transport in Plants: New Players and Their Potential RolesGerd P. Bienert and Thomas P. JahnAbstractIntroductionThe Challenge of As Speciation in PlantsTransport of As in PlantsWhat Do the Different ¿Omics¿ Tell Us About NIP?Mediated As Transmembrane Transport?The Physiological Role of NIPsPlant NIPs Transport Trivalent AntimonyConclusion10. Major Intrinsic Proteins in Biomimetic MembranesClaus Hélix NielsenAbstractIntroductionBiomimetic MembranesMIP Biomimetic Membranes and Osmotic ProcessesConclusionIndex