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Exploring the molecular landscape of Chlamydomonas with in situ cryo-electron tomography

Jeudi 23 novembre 2017 11:00 - Duree : 1 heure
Lieu : Salle d’accueil du CEA-Grenoble

Orateur : Ben ENGEL (Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany)

We are leveraging new advances in cryo-electron tomography (cryo-ET) to investigate macromolecular complexes within the native cellular environment. Thin slices of vitrified Chlamydomonas reinhardtii cells are prepared by cryo-focused ion beam (cryo-FIB) milling and then imaged by state-of-the-art cryo-ET. The resulting 3D views of cellular volumes have provided new insights into the molecular organization of organelles. Within the chloroplast, we identified fine membrane tubules that likely serve as conduits for the directed diffusion of metabolites between the pyrenoid and the chloroplast stroma. We were also able to directly visualize photosynthetic complexes within native thylakoid membranes, as well as the organization of RuBisCO complexes in the pyrenoid. At the nuclear envelope, we observed that proteasomes encircle nuclear pore complexes (NPCs), binding both to the inner nuclear membrane and the NPC basket, likely performing quality control of nucleocytoplasmic exchange. Subtomogram averaging of the NPC revealed that it assembles in a novel asymmetric oligomeric state, while averaging of ER-bound ribosomes enabled us to dissect the molecular architecture of the TRAP translocon component. In the Golgi, we identified protein arrays that establish the narrow membrane spacing of the trans-Golgi cisternae, and also solved the in situ structure of the COPI coat complex. In addition to the in situ characterization of individual macromolecular complexes, in the future we will aim for a visual proteomics approach to identify and classify every macromolecule within the cellular volumes.

- Albert S, Schaffer M, Beck F, Mosalaganti S, Asano S, Thomas HF, Plitzko JM, Beck M, Baumeister W and Engel BD. Proteasomes tether to two distinct sites at the nuclear pore complex. PNAS, 2017, In press.

- Bykov YS, Schaffer M, Dodonova SO, Albert S, Plitzko JM, Baumeister W, Engel BD and Briggs JAG. The structure of the COPI coat determined within the cell. eLife, 2017, In press.

- Freeman Rosenzweig ES, Xu B, Kuhn Cuellar L, Martinez-Sanchez A, Schaffer M, Strauss M, Cartwright HN, Ronceray P, Plitzko JM, Förster F, Wingreen NS, Engel BD, Mackinder LCM and Jonikas MC. The eukaryotic CO2-concentrating organelle is liquid-like and exhibits dynamic reorganization. Cell, 2017

- Pfeffer S, Dudek J, Schaffer M, Ng BG, Albert S, Plitzko JM, Baumeister W, Zimmermann R, Freeze HH, Engel BD and Förster. Dissecting the molecular organization of the translocon-associated protein complex. Nature Communications, 2017

- Schaffer M, Mahamid J, Engel BD, Laugks T, Baumeister W and Plitzko J. Optimized cryo-focused ion beam sample preparation aimed at in situ structural studies of membrane proteins. Journal of Structural Biology, 2017

- Asano S, Engel BD and Baumeister W. In situ cryo-electron tomography : A post-reductionist approach to structural biology. Journal of Molecular Biology, 2016

- Engel BD, Schaffer M, Albert S, Asano S, Plitzko JM and Baumeister W. In situ structural analysis of Golgi intracisternal protein arrays. PNAS, 2015

- Engel BD, Schaffer M, Cuellar LK, Villa E, Plitzko JM and Baumeister W. Native architecture of the Chlamydomonas chloroplast revealed by in situ cryo-electron tomography. eLife, 2015

Contact : odile.rossignol@cea.fr

Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (BIG ex-iRSTV)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire BIG)
Site de l'évènement : Site CEA sans badge requis

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