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High-speed atomic force microscopy: cooperative adhesion and dynamic equilibrium of junctional microdomain membrane proteins.

Abstract : Junctional microdomains, paradigm for membrane protein segregation in functional assemblies, in eye lens fiber cell membranes are constituted of lens-specific aquaporin-0 tetramers (AQP0(4)) and connexin (Cx) hexamers, termed connexons. Both proteins have double function to assure nutrition and mediate adhesion of lens cells. Here we use high-speed atomic force microscopy to examine microdomain protein dynamics at the single-molecule level. We found that the adhesion function of head-to-head associated AQP0(4) and Cx is cooperative. This finding provides first experimental evidence for the mechanistic importance for junctional microdomain formation. From the observation of lateral association-dissociation events of AQP0(4), we determine that the enthalpic energy gain of a single AQP0(4)-AQP0(4) interaction in the membrane plane is -2.7 k(B)T, sufficient to drive formation of microdomains. Connexon association is stronger as dynamics are rarely observed, explaining their rim localization in junctional microdomains.
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https://www.hal.inserm.fr/inserm-01363148
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Adai Colom, Ignacio Casuso, Thomas Boudier, Simon Scheuring. High-speed atomic force microscopy: cooperative adhesion and dynamic equilibrium of junctional microdomain membrane proteins.. Journal of Molecular Biology, Elsevier, 2012, 423 (2), pp.249-56. ⟨10.1016/j.jmb.2012.07.004⟩. ⟨inserm-01363148⟩

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