Shape matters in protein mobility within membranes Quemeneur, François; Sigurdsson, Jon K.; Renner, Marianne ...
Proceedings of the National Academy of Sciences - PNAS,
04/2014, Letnik:
111, Številka:
14
Journal Article
Recenzirano
Odprti dostop
The lateral mobility of proteins within cell membranes is usually thought to be dependent on their size and modulated by local heterogeneities of the membrane. Experiments using single-particle ...tracking on reconstituted membranes demonstrate that protein diffusion is significantly influenced by the interplay of membrane curvature, membrane tension, and protein shape. We find that the curvature-coupled voltage-gated potassium channel (KvAP) undergoes a significant increase in protein mobility under tension, whereas the mobility of the curvature-neutral water channel aquaporin 0 (AQP0) is insensitive to it. Such observations are well explained in terms of an effective friction coefficient of the protein induced by the local membrane deformation.
Mobility in geometrically confined membranes Domanov, Yegor A; Aimon, Sophie; Toombes, Gilman E.S ...
Proceedings of the National Academy of Sciences - PNAS,
08/2011, Letnik:
108, Številka:
31
Journal Article
Recenzirano
Odprti dostop
Lipid and protein lateral mobility is essential for biological function. Our theoretical understanding of this mobility can be traced to the seminal work of Saffman and Delbrück, who predicted a ...logarithmic dependence of the protein diffusion coefficient (i) on the inverse of the size of the protein and (ii) on the "membrane size" for membranes of finite size Saffman P, Delbrück M (1975) Proc Natl Acad Sci USA 72:3111--3113. Although the experimental proof of the first prediction is a matter of debate, the second has not previously been thought to be experimentally accessible. Here, we construct just such a geometrically confined membrane by forming lipid bilayer nanotubes of controlled radii connected to giant liposomes. We followed the diffusion of individual molecules in the tubular membrane using single particle tracking of quantum dots coupled to lipids or voltage-gated potassium channels KvAP, while changing the membrane tube radius from approximately 250 to 10 nm. We found that both lipid and protein diffusion was slower in tubular membranes with smaller radii. The protein diffusion coefficient decreased as much as 5-fold compared to diffusion on the effectively flat membrane of the giant liposomes. Both lipid and protein diffusion data are consistent with the predictions of a hydrodynamic theory that extends the work of Saffman and Delbrück to cylindrical geometries. This study therefore provides strong experimental support for the ubiquitous Saffman-Delbrück theory and elucidates the role of membrane geometry and size in regulating lateral diffusion.
Fondé au début de la Seconde Guerre mondiale au sein des mouvements de jeunesse protestants, le Comité inter-mouvements auprès des évacués, devenu Cimade - service œcuménique d’entraide, s’est ...imposé, en soixante-dix ans d’histoire, comme l’une des principales associations françaises intervenant auprès des migrants et des réfugiés. L’inventaire et l’ouverture de ses archives, déposées à la Bibliothèque de documentation internationale contemporaine en 2007, ont ouvert la voie à de nouvelles recherches et conduit à l’organisation en 2010 d’un colloque centré sur le refuge à l’origine de cet ouvrage collectif. Cette première plongée dans les archives interroge l’identité de la Cimade et son évolution, entre engagement, ancrage au sein du protestantisme, rapport au politique et intervention dans le champ public. Elle permet aussi d’investir les questionnements actuels sur le monde associatif militant et sur la politique de l’asile, des années fondatrices de la Seconde Guerre mondiale à la « crise de l’asile » de la décennie 1990.
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