Cryo-EM Studies of Dynamin Mediated Membrane Constriction

Abstract

Dynamin is a mechanochemical GTPase that mediates endocytosis by catalyzing membrane fission to release vesicles. Dynamin therefore plays a prominent role in signaling processes especially at the neural synapse where it facilitates synaptic recycling. Defects in dynamin have been associated with centronulcear myopathy and Charcot-Marie-Tooth neuropathy. Furthermore, viruses such as influenza and Hepatitis C infect cells through a dynamin dependent mechanism. Structural studies over the past 20 years have revealed key snapshots of dynamin as it catalyzes membrane fission. First, dynamin self-assembles into highly ordered, helical scaffolds around the lipid membrane. Then, GTP binding and hydrolysis induce conformational changes in dynamin that leads to membrane constriction and fission. While crystal structures are available of lipid-free dynamin oligomers, obtaining high-resolution structures of dynamin helical assemblies on lipid tubes have been hampered by sample heterogeneity. Here, we examined high-resolution data collected from a Gatan K2 summit camera on a FEI Tecnai F20 and a Titan Krios electron microscope to elucidate the complex helical transitions of dynamin. Our analyses of various dynamin mutants and nucleotide-bound states capture the molecular details of dynamin mediated membrane constriction and fission.