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 Molecular Anatomy of Synaptic Vesicles |
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A Brownian Dynamics Interpretation of Membrane Protein Clustering
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Carsten Kutzner and Helmut Grubmüller
in collaboration with Jochen J. Sieber, Katrin I. Willig, Claas Gerding-Reimers, Benjamin Harke, Gerald Donnert, Burkhard Rammner, Christian Eggeling, Stefan W. Hell, and Thorsten Lang
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Most plasmalemmal proteins organize in submicrometer-sized clusters whose architecture and dynamics are still enigmatic. With syntaxin 1 as an example, we applied a combination of far-field optical nanoscopy, biochemistry, fluorescence recovery after photobleaching (FRAP) analysis, and simulations to show that clustering can be explained by self-organization based on simple physical principles. On average, the syntaxin clusters exhibit a diameter of 50 to 60 nanometers and contain 75 densely crowded syntaxins that dynamically exchange with freely diffusing molecules. Self-association depends on weak homophilic protein-protein interactions. Our simulations suggest that clustering immobilizes and conformationally constrains the molecules. Moreover, a balance between self-association and crowding-induced steric repulsions is sufficient to explain both the size and dynamics of syntaxin clusters and likely of many oligomerizing membrane proteins that form supramolecular structures.
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Click on the right-hand picture to watch the diffusion of the syntaxin molecules on the membrane while they produce the flourescence recovery curve. The modeled recovery curve (green) is able to reproduce the experimental result (red) very closely.
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References
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J. J. Sieber, K. I. Willig, C. Kutzner, C. Gerding-Reimers, B. Harke, G. Donnert, B. Rammner, C. Eggeling, S. W. Hell, H. Grubmüller, and T. Lang (2007).
Anatomy and Dynamics of a Supramolecular Membrane Protein Cluster.
Science 317: 1072-1076
[syntaxin-pdf]
[header-pdf]
[perspective-pdf]
[supplement-pdf]
There is also a talk by C. Kutzner available on that topic [pdf]
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