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Membrane constriction by Dynamin

Summary

Science

Data

The Dynamin tetramer binds a membrane and forms a filament, a right-handed helix around a membrane tube. The proposed stepping mechanism for membrane constriction involves a power stroke, that pulls the helical turns against each other, each step reducing the membrane tube radius by approximately 1 nm.
The animation introduces the domain structure of dynamin and the way it forms dimers and then a tetramer out of two dimers. The helical filament formation is shown from the front and the top, followed by the dimer formation of two G-domains from neighbouring turns. For the first power stroke the sequence of events are shown individually, for the second and third steps in a more synchronous coincidential way.

This was a project for and with Katja Faelber, Jeffrey Noel and Oliver Daumke - Max Delbrück Center for Molecular Medicine (MDC), Berlin.

status: 2019

Dynamin is a five-domain protein, four of which have been structurally characterized. GTP binding shifts the G-domain/BSE to an open conformation. The Stalk domains mediate the formation of a stable dimer. The dimer mediates further oligomerization through its tetramer interface. In solution, oligomerization stops with the tetramer. The PH-domains mediate membrane binding. Localization to the membrane opens up the tetrameric interface for filament formation. The tetramer has a naturally curved shape, corresponding to the curvature of tight membrane necks, but can additionally adjust its curvature. The filament forms a right-handed helix around a membrane tube. The proposed stepping mechanism for membrane constriction: After one helical turn has formed, GTP-bound G-domains from neighbouring turns dimerize. Dimerization activates GTP hydrolysis, which generates a strong shift in the G-domain/ BSE to the closed conformation. This re-arrangement comprises the power stroke, pulling the helical turns against each other. This constricts the underlying membrane tube. After phosphate release the GDP-bound dimer is destabilized and dissociates, allowing GDP to be released. This makes the nucleotide pocket available for GTP binding, which initiates the recovery stroke. The G domain is now in position to dimerize with the next G-domain along the filament and performs more steps, each step reducing the membrane tube radius by approximately 1 nm.