title: A hemi-fission intermediate links two mechanistically distinct stages of membrane fission.
abstract: Fusion and fission drive all vesicular transport. Although topologically opposite, these reactions pass through the same hemi-fusion/fission intermediate, characterized by a 'stalk' in which only the outer membrane monolayers of the two compartments have merged to form a localized non-bilayer connection. Formation of the hemi-fission intermediate requires energy input from proteins catalysing membrane remodelling; however, the relationship between protein conformational rearrangements and hemi-fusion/fission remains obscure. Here we analysed how the GTPase cycle of human dynamin 1, the prototypical membrane fission catalyst, is directly coupled to membrane remodelling. We used intramolecular chemical crosslinking to stabilize dynamin in its GDP·AlF4(-)-bound transition state. In the absence of GTP this conformer produced stable hemi-fission, but failed to progress to complete fission, even in the presence of GTP. Further analysis revealed that the pleckstrin homology domain (PHD) locked in its membrane-inserted state facilitated hemi-fission. A second mode of dynamin activity, fuelled by GTP hydrolysis, couples dynamin disassembly with cooperative diminishing of the PHD wedging, thus destabilizing the hemi-fission intermediate to complete fission. Molecular simulations corroborate the bimodal character of dynamin action and indicate radial and axial forces as dominant, although not independent, drivers of hemi-fission and fission transformations, respectively. Mirrored in the fusion reaction, the force bimodality might constitute a general paradigm for leakage-free membrane remodelling.
authors.affiliation: Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75201.
authors.forename: Juha-Pekka
authors.initials: JP
authors.lastname: Mattila
authors.affiliation: Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of The Basque Country, Leioa, Spain.
authors.forename: Anna V
authors.initials: AV
authors.lastname: Shnyrova
authors.affiliation: Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892.
authors.forename: Anna C
authors.initials: AC
authors.lastname: Sundborger
authors.affiliation: Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of The Basque Country, Leioa, Spain.
authors.forename: Eva Rodriguez
authors.initials: ER
authors.lastname: Hortelano
authors.affiliation: Institute for Theoretical Physics, Georg-August University, 37077 Göttingen, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Fuhrmans
authors.affiliation: Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Neumann
authors.affiliation: Institute for Theoretical Physics, Georg-August University, 37077 Göttingen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Müller
authors.affiliation: Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892.
authors.forename: Jenny E
authors.initials: JE
authors.lastname: Hinshaw
authors.affiliation: Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75201.
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Schmid
authors.affiliation: Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of The Basque Country, Leioa, Spain.|IKERBASQUE, Basque Foundation of Science, Bilbao, Spain.
authors.forename: Vadim A
authors.initials: VA
authors.lastname: Frolov
mesh_terms: D055162:Biocatalysis; D001798:Blood Proteins / Q000737:chemistry; D002462:Cell Membrane / Q000378:metabolism*; D022162:Cytoplasmic Vesicles / Q000378:metabolism*; D034284:Dynamin I / Q000737:chemistry / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008561:Membrane Fusion; D008958:Models, Molecular; D010750:Phosphoproteins / Q000737:chemistry; D011487:Protein Conformation
chemical_list: D001798:Blood Proteins; D010750:Phosphoproteins; C039077:platelet protein P47; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D034284:Dynamin I