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BP: Fachverband Biologische Physik

BP 18: Regulation and Signaling

BP 18.2: Hauptvortrag

Donnerstag, 26. März 2009, 10:00–10:30, HÜL 186

Towards an understanding of membrane and protein traffic in living cells — •Matthias Weiss — Cellular Biophysics Group, German Cancer Research Center, Heidelberg, Germany

Sorting of transmembrane proteins is a central task of the secretory pathway in eucaryotic cells. Here, the multitude of transmembrane proteins have to utilize self-organization processes on the molecular scale to decide whether they participate in transport along the secretory pathway or rather reside in their current compartment (e.g. the endoplasmic reticulum, ER, or the Golgi apparatus, GA). Using advanced light microscopy techniques and coarse-grained membrane simulations, we have addressed two of the key issues in membrane and protein trafficking. First, we elucidated the interaction between unfolded proteins and chaperones in the ER. As a result, we found that unfolded proteins show a strongly obstructed diffusion that can be altered to the diffusion behavior of folded proteins, e.g. by blocking the interaction with chaperones. Accompanying simulations indicate that this behavior reflects the obstructed diffusion of a cluster of chaperones and unfolded proteins due to (almost immobile) translocon pores in the ER. Second, we asked for generic mechanisms that support the sorting of folded transmembrane proteins into emerging vesicules at the ER and/or the GA. We showed by means of coarse-grained membrane simulations that hydrophobic mismatching can drive cluster formation of transmembrane proteins and even the demixing of a heterogeneous population of proteins. Based on this result, we propose a generic way to make and fill vesicular carriers with a well-defined cargo of proteins.