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Caractérisation Structurale et Fonctionnelle de l'Aquaglycéroporine AQP3 exprimée dans divers Systèmes

Abstract : Proteins of the MIP family are membrane proteins that facilitate water or/and solute transport across biological membranes. The members of this family have been classified in three subgroups according to their sequence similarity and function: the aquaporins contains water selective transport proteins (AQP1, AQP2,...), the aquaglyceroporins are water and solute permeable proteins such as AQP3, and the glycerol facilitators are impermeable to water. We have shown that the glycerol permeability of red blood cell membrane is due to the presence of AQP3. In order to determine parts of the proteins involved in the selectivity, we have constructed chimeras between AQP2 and AQP3. Permeability measurements of oocyte expressing AQP3-AQP2 Cter showed that the C terminal extremity is critical for the transport of water but not for the glycerol one. Comparing the water and glycerol transports of oocytes at various stages of maturation, we have shown that an endogenous channel or transporter was present in immature oocytes. Our interest was then focused on the determination of the oligomerization status of an aquaglyceroporin: AQP3, in different membranes. The known tetrameric structure of AQP1 was observed by velocity sedimentation on sucrose gradient, in contrast, AQP3 was found in much slighter fraction in monomeric and dimeric forms. The dimer seems to be very resistant to SDS and hydrophilic reducing agent treatment. Due to a plausible sensitivity of AQP3 to the non-denaturant detergents used, we could not exclude its tetrameric form in the membrane. The results obtained with electronic microscopy on AQP1 and AQP3 expressing oocyte membrane cryofracture showed that AQP1 and AQP3 IMP sizes were not different enough to suggest another membrane organization.
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https://tel.archives-ouvertes.fr/tel-00004048
Contributor : Nathalie Roudier <>
Submitted on : Monday, December 22, 2003 - 2:12:06 PM
Last modification on : Thursday, June 4, 2020 - 4:22:03 PM
Long-term archiving on: : Wednesday, September 12, 2012 - 12:10:26 PM

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  • HAL Id : tel-00004048, version 1

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Nathalie Roudier. Caractérisation Structurale et Fonctionnelle de l'Aquaglycéroporine AQP3 exprimée dans divers Systèmes. Biochimie [q-bio.BM]. Université Paris Sud - Paris XI, 2000. Français. ⟨tel-00004048⟩

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