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Insights into the Selectivity Mechanisms of Grapevine NIP Aquaporins.

ABSTRACT: Nodulin 26-like intrinsic proteins (NIPs) of the plant aquaporin family majorly facilitate the transport of physiologically relevant solutes. The present study intended to investigate how substrate selectivity in grapevine NIPs is influenced by the aromatic/arginine (ar/R) selectivity filter within the pore and the possible underlying mechanisms. A mutational approach was used to interchange the ar/R residues between grapevine NIPs (VvTnNIP1;1 with VvTnNIP6;1, and VvTnNIP2;1 with VvTnNIP5;1). Their functional characterization by stopped-flow spectroscopy in Saccharomyces cerevisiae revealed that mutations in residues of H2/H5 helices in VvTnNIP1;1 and VvTnNIP6;1 caused a general decline in membrane glycerol permeability but did not impart the expected substrate conductivity in the mutants. This result suggests that ar/R filter substitution could alter the NIP channel activity, but it was not sufficient to interchange their substrate preferences. Further, homology modeling analyses evidenced that variations in the pore radius combined with the differences in the channel's physicochemical properties (hydrophilicity/hydrophobicity) may drive substrate selectivity. Furthermore, yeast growth assays showed that H5 residue substitution alleviated the sensitivity of VvTnNIP2;1 and VvTnNIP5;1 to As, B, and Se, implying importance of H5 sequence for substrate selection. These results contribute to the knowledge of the overall determinants of substrate selectivity in NIPs.

SUBMITTER: Sabir F

PROVIDER: S-EPMC7576499 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Insights into the Selectivity Mechanisms of Grapevine NIP Aquaporins.

Sabir Farzana F Di Pizio Antonella A Loureiro-Dias Maria C MC Casini Angela A Soveral Graça G Prista Catarina C

International journal of molecular sciences 20200913 18

Nodulin 26-like intrinsic proteins (NIPs) of the plant aquaporin family majorly facilitate the transport of physiologically relevant solutes. The present study intended to investigate how substrate selectivity in grapevine NIPs is influenced by the aromatic/arginine (ar/R) selectivity filter within the pore and the possible underlying mechanisms. A mutational approach was used to interchange the ar/R residues between grapevine NIPs (VvTnNIP1;1 with VvTnNIP6;1, and VvTnNIP2;1 with VvTnNIP5;1). Th ...[more]

PMID: 32933135

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Project description:IntroductionNodulin-26-like intrinsic proteins (NIPs) are integral membrane proteins belonging to the aquaporin family, that facilitate the transport of neutral solutes across the bilayer. The OsNIP2;1 a member of NIP-III class of aquaporins is permeable to beneficial elements like silicon and hazardous arsenic. However, the atomistic cross-talk of these molecules traversing the OsNIP2;1 channel is not well understood.ObjectiveDue to the lack of genomic variation but the availability of high confidence crystal structure, this study aims to highlight structural determinants of metalloid permeation through OsNIP2;1.MethodsThe molecular simulations, combined with site-directed mutagenesis were used to probe the role of specific residues in the metalloid transport activity of OsNIP2;1.ResultsWe drew energetic landscape of OsNIP2;1, for silicic and arsenous acid transport. Potential Mean Force (PMF) construction illuminate three prominent energetic barriers for metalloid passage through the pore. One corresponds to the extracellular molecular entry in the channel, the second located on ar/R filter, and the third size constriction in the cytoplasmic half. Comparative PMF for silicic acid and arsenous acid elucidate a higher barrier for silicic acid at the cytoplasmic constrict resulting in longer residence time for silicon. Furthermore, our simulation studies explained the importance of conserved residues in loop-C and loop-D with a direct effect on pore dynamics and metalloid transport. Next we assessed contribution of predicted key residues for arsenic uptake, by functional complementation in yeast. With the aim of reducing arsenic uptake while maintaining beneficial elements uptake, we identified novel OsNIP2;1 mutants with substantial reduction in arsenic uptake in yeast.ConclusionWe provide a comprehensive assessment of pore lining residues of OsNIP2;1 with respect to metalloid uptake. The findings will expand mechanistic understanding of aquaporin's metalloid selectivity and facilitate variant interpretation to develop novel alleles with preference for beneficial metalloid species and reducing hazardous ones.

Project description:Gene expression analyses have been performed on brain, liver and muscle of eels (Anguilla anguilla) sampled in three different segment of the Canal des Etangs ( artificial canal linking Arcachon Basin and Lacanau Lake). The present study relies on intraspecific differences of glass eels encountered below and above the water dams. Eels were collected using electric fishing under similar climatic and hydrological conditions. Individuals were sampled below the obstacle, close to the fishway entry in segment 1 (Pas du Bouc; +44° 50' 27.95, -1° 9' 8.09) and 2 (Langouarde, +44° 51' 32.92, -1° 9' 5.03). Fish from the segment 3 (Joncru; +44° 52' 57.13, -1° 8' 11.70) were sampled on the fishway, as water depth before the obstacle, approximately 2 meters, precluded the use of electro-fishing technique. Ten individuals were selected from each site according to their body size (between 83 and 155 mm) and health status (no externally visible pathogens) criteria. Internal parasites such as Anguilicola crassus were taken into account. Sampled and selected fish were immediately sacrified by decapitation and the whole brain, liver and muscle tissue (posterior bottom body part) were dissected and stored at -80°C in separate tubes with RNAlater buffer (Quiagen) for gene expression analysis. Microarray analysis was conducted using an European eel-specific array consisting of a total of 14,913 probes based on a large collection of high-throughput transcriptomic sequences (Pujolar et al. 2012). Probe sequences and further details on the microarray platform can be found on the GEO database under accession number GPL15124. A comparative analysis of gene expression was conducted between eels sampled in differents segments of Canal des Etangs. Total RNAs were extracted from the whole liver,muscle and brain using the Absolutely RNA RT-PCR Miniprep kit (Agilent) according to the manufacturer’s instructions. Three independent RNA pools, each consisting of three individuals RNA samples, were prepared for each sampling site and tissues. Due to technical problems, it was no possible to perform microarray analyses in muscle of eels sampled in forebay 3. Accordingly, DNA microarray analysis has been performed in a total of 24 pools. RNAs’ quality was evaluated by electrophoresis on a 1% agarose gel and their concentrations were determined by spectrophotometry. Total RNA was stored in RNAse free water at -80° C. Sample labelling and hybridization were conducted following the details in Pujolar et al. (2012). Hybridized slides were scanned at 5 µm resolution using an Agilent DNA microarray scanner. Slides were scanned at two different sensitivity levels (XDR Hi 100% and XDR Lo 10%) and the two linked images generated were analysed together. Data were extracted and background subtracted using the standard procedure in Agilent Feature Extraction (FE) software v. 9.5.1. Data were normalized separately for each tissue using a quantile normalization procedure using R (http://www.r-project.org).

Dataset Information

Insights into the Selectivity Mechanisms of Grapevine NIP Aquaporins.

Publications

Insights into the Selectivity Mechanisms of Grapevine NIP Aquaporins.

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