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Comparison of the structure of a potassium channel in both 2D and 3D crystals

Vendredi 14 juin 2013 11:00 - Duree : 1 heure
Lieu : Salle des séminaires de l’IBS - J.P. Ebel - 41 rue Jules Horowitz - Grenoble

Orateur : Catherine VENIEN-BRYAN (Institut de Minéralogie et de Physique des Milieux Condensés, Paris)

Inwardly-rectifying potassium (Kir) channels regulate membrane electrical excitability and K+ transport in many cell types where they control such diverse processes as heart rate, vascular tone, insulin secretion and salt/fluid balance. Their physiological importance is highlighted by the fact that genetically inherited defects in Kir channels are responsible for a wide-range of channelopathies. To elucidate how channel function becomes defective in the disease state requires a detailed understanding of channel structure in both the open and closed states. Here for the first time, we report the structure of a KirBac potassium channel with an open bundle crossing indicating a mechanism of channel gating determined by X-ray crystallography at 3Å resolution. In this model, the rotational twist of the cytoplasmic domain is coupled to opening of the bundle-crossing gate via a network of inter- and intra-subunit interactions. In addition, we have also used EM analysis of 2D crystals of the same Kir channel trapped in an open state and compared these results with the 3D structure. Intriguingly, the projection maps from the EM experiments suggest a larger opening of the pore in the 2D crystal form compared to that observed in the 3D crystal structure. The organization of these two crystal forms is different and suggests that the 2D crystals may permit stabilisation of an open state structure that is not compatible with 3D crystallisation. These results not only have major implications for our understanding of the open state structure of the Kir channel, but more importantly they demonstrate the general utility and importance of methods such as electron microscopy and 2D crystallography for the study of membrane protein structure.

Contact : odile.kaikati@ibs.fr

Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (IBS)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire IBS)
Site de l'évènement : Polygone scientifique

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