Proton transport mechanism in the cell membrane of Xenopus laevis oocytes

1992 ◽  
Vol 420 (1) ◽  
pp. 78-82 ◽  
Author(s):  
Birgitta-Christina Burckhardt ◽  
Beate Kroll ◽  
Eberhard Fr�mter
Keyword(s):  
Cell Membrane ◽  
Xenopus Laevis ◽  
Proton Transport ◽  
Transport Mechanism ◽  
Xenopus Laevis Oocytes

scholarly journals Coupling Modes and Stoichiometry of Cl−/HCO3− Exchange by slc26a3 and slc26a6

2006 ◽  
Vol 127 (5) ◽  
pp. 511-524 ◽  
Author(s):  
Nikolay Shcheynikov ◽  
Youxue Wang ◽  
Meeyoung Park ◽  
Shigeru B.H. Ko ◽  
Michael Dorwart ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Xenopus Laevis ◽  
Transport Mechanism ◽  
Xenopus Laevis Oocytes ◽  
Human Embryonic Kidney ◽  
Apparent Affinity ◽  
293 Cells ◽  
The Family ◽  
Flux Measurements ◽  
Free Media

The SLC26 transporters are a family of mostly luminal Cl− and HCO3− transporters. The transport mechanism and the Cl−/HCO3− stoichiometry are not known for any member of the family. To address these questions, we simultaneously measured the HCO3− and Cl− fluxes and the current or membrane potential of slc26a3 and slc26a6 expressed in Xenopus laevis oocytes and the current of the transporters expressed in human embryonic kidney 293 cells. slc26a3 mediates a coupled 2Cl−/1HCO3− exchanger. The membrane potential modulated the apparent affinity for extracellular Cl− of Cl−/HCO3− exchange by slc26a3. Interestingly, the replacement of Cl− with NO3− or SCN− uncoupled the transport, with large NO3− and SCN− currents and low HCO3− transport. An apparent uncoupled current was also developed during the incubation of slc26a3-expressing oocytes in HCO3−-buffered Cl−-free media. These findings were used to develop a turnover cycle for Cl− and HCO3− transport by slc26a3. Cl− and HCO3− flux measurements revealed that slc26a6 mediates a 1Cl−/2HCO3− exchange. Accordingly, holding the membrane potential at 40 and −100 mV accelerated and inhibited, respectively, Cl−-mediated HCO3− influx, and holding the membrane potential at −100 mV increased HCO3−-mediated Cl− influx. These findings indicate that slc26a6 functions as a coupled 1Cl−/2HCO3− exchanger. The significance of isoform-specific Cl− and HCO3− transport stoichiometry by slc26a3 and slc26a6 is discussed in the context of diseases of epithelial Cl− absorption and HCO3− secretion.

scholarly journals A new system to evaluate characteristics of Niemann-Pick C1 Like 1-mediated cholesterol transport using Xenopus laevis oocytes

2021 ◽  
Vol 1863 (2) ◽  
pp. 183508
Author(s):  
Shunsuke Nashimoto ◽  
Saori Yagi ◽  
Naoki Takeda ◽  
Miku Nonaka ◽  
Yoh Takekuma ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Cholesterol Transport ◽  
Xenopus Laevis Oocytes ◽  
Niemann Pick ◽  
New System

Characterization of Transport Activity of SLC11 Transporters in Xenopus laevis Oocytes by Fluorophore Quenching

2021 ◽  
pp. 247255522110041
Author(s):  
Raffaella Cinquetti ◽  
Francesca Guia Imperiali ◽  
Salvatore Bozzaro ◽  
Daniele Zanella ◽  
Francesca Vacca ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Voltage Clamp ◽  
Expression System ◽  
Peptide Transporter ◽  
Xenopus Laevis Oocytes ◽  
Substrate Uptake ◽  
Transport Activity ◽  
Experimental Conditions ◽  
Metal Transporters ◽  
Electrode Voltage

Membrane proteins are involved in different physiological functions and are the target of pharmaceutical and abuse drugs. Xenopus laevis oocytes provide a powerful heterologous expression system for functional studies of these proteins. Typical experiments investigate transport using electrophysiology and radiolabeled uptake. A two-electrode voltage clamp is suitable only for electrogenic proteins, and uptake measurements require the existence of radiolabeled substrates and adequate laboratory facilities. Recently, Dictyostelium discoideum Nramp1 and NrampB were characterized using multidisciplinary approaches. NrampB showed no measurable electrogenic activity, and it was investigated in Xenopus oocytes by acquiring confocal images of the quenching of injected fluorophore calcein. This method is adequate to measure the variation in emitted fluorescence, and thus transporter activity indirectly, but requires long experimental procedures to collect statistically consistent data. Considering that optimal expression of heterologous proteins lasts for 48–72 h, a slow acquiring process requires the use of more than one batch of oocytes to complete the experiments. Here, a novel approach to measure substrate uptake is reported. Upon injection of a fluorophore, oocytes were incubated with the substrate and the transport activity measured, evaluating fluorescence quenching in a microplate reader. The technique permits the testing of tens of oocytes in different experimental conditions simultaneously, and thus the collection of significant statistical data for each batch, saving time and animals. The method was tested with different metal transporters (SLC11), DMT1, DdNramp1, and DdNrampB, and verified with the peptide transporter PepT1 (SLC15). Comparison with traditional methods (uptake, two-electrode voltage clamp) and with quenching images acquired by fluorescence microscopy confirmed its efficacy.

scholarly journals Proton Transport Mechanism and Pathways in the Superprotonic Phase of M3H(AO4)2 Solid Acids from Ab Initio Molecular Dynamics Simulations

2021 ◽  
Author(s):  
Boris Merinov ◽  
Sergey Morozov
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Proton Transport ◽  
Transport Mechanism ◽  
Solid Acids ◽  
Ab Initio Molecular Dynamics ◽  
Theoretical Studies ◽  
Dynamics Simulations ◽  
Experimental And Theoretical Studies ◽  
Superprotonic Phase

The proton transport mechanism in superprotonic phases of solid acids is a subject of experimental and theoretical studies for a number of years. Despite this, details of the mechanism still...

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