Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

38-POS Board 38 UNDERSTANDING DYNAMIN CONSTRICTION VIA PROCESSIVE STEPPING Jeffrey Noel 1 ; Oleg Ganichkin 1 ; Alexander Mikhailov 2 ; Oliver Daumke 1,3 ; 1 Max Delbrueck Center, Berlin, Germany 2 Kanazawa University, Nano Life Science Institute, Kanazawa, Ishikawa, Japan 3 Freie Universitat, Berlin, Germany The final scission step in clathrin-mediated endocytosis is catalyzed by the molecular machine dynamin. While there have been many suggestions for how the final topological change of the membrane tube is effected, all proposals assume some degree of constriction by dynamin. We quantify the elasticity of the dynamin polymer and conclude that passive elastic deformation of the tube is likely insufficient to reach sufficiently small radii for scission. Thus, as discussed over the past decade, dynamin must use GTP to actively deform the membrane. We show through molecular modeling that the conformational change between the G-domain and BSE induced by GTP hydrolysis is sufficiently large to allow for a processive stepping motion between helical turns. We further characterize the G-domain/BSE motion with single-molecule FRET and stopped-flow kinetic measurements. These experimental inputs and detailed molecular simulations are combined into a polymer simulation that can explore the interaction of many G- domains simultaneously. We show that under certain conditions, the dynamin model can perform processive stepping leading to constriction of its membrane tube template.

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