Anatomy and Dynamics of a Supramolecular Membrane Protein Cluster

• DOI: 10.1126/science.1141727
• Publication Date: 2007-08-23T20:53:54Z
• Authors: Jochen J. Sieber; Katrin I. Willig; Carsten Kutzner; Claas Gerding-Rei...; Benjamin Harke; Gerald Donnert; Burkhard Rammner; Christian Eggeling; Stefan W. Hell; Helmut Grubmüller; Thorsten Lang
• Keywords: 0301 basic medicine; ddc:610; Microscopy, Confocal; Chemical Phenomena; Chemistry, Physical; Recombinant Fusion Proteins; Amino Acid Motifs; Cell Membrane; Green Fluorescent Proteins; Immunoblotting; Syntaxin 1; Models, Biological; PC12 Cells; Protein Structure, Tertiary; Rats; Diffusion; 03 medical and health sciences; Microscopy, Fluorescence; Animals; Nanotechnology; Computer Simulation; Fluorescence Recovery After Photobleaching

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. 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.