Mitochondrial genome maintenance protein 1 (Mgm1) is thought to create filaments preferring a left-handed helix and positive curvature. In this geometry, a dynamin-like power stroke would lead to an expansion of the filament, and thus, an expansion of the membrane tube. However, Mgm1 may create other filament geometries and bind a membrane surface with negative curvature.
The animation introduces the domain structure, dimerisation and tetramerisation. It shows models all four possibilities for right-handed and left-handed helical filament formation and both for membranes with positive and negative curvature. The identical power stroke then either would lead to constriction or expansion of the membrane tube.
This was a project for and with: Katja Faelber, Jeffrey Noel and Oliver Daumke - Max Delbrück Center for Molecular Medicine (MDC), Berlin. An extract of this animation was published as supplementary video in Faelber et al. Nature, 571:429-433 (2019).
status: 2019
Mitochondrial genome maintenance protein 1 (Mgm1) is a homologue of the human OPA1 protein. The crystal structure has four domains. The stalk mediates the formation of a strong dimer. An additional stalk interface connects two dimers into a tetramer. The paddle domains control the protein’s membrane-binding affinity. Crystallography and cryo-EM suggest that the tetramer interface creates filaments preferring a left-handed helix and positive curvature. In this geometry, a dynamin-like power stroke would lead to an expansion of the filament, and thus, an expansion of the membrane tube. However, in a cellular context Mgm1 may create other filament geometries. A right-handed filament would function similarly to dynamin, and constrict the underlying membrane tube.
Importantly, Mgm1 is a modulator of the shape of mitochondrial cristae. Near a cristae junction, the membrane geometry resembles the inside of a membrane tube where the membrane surface has negative curvature. Membrane binding at the inside of a tube switches the effect of the power stroke . Now a left-handed helix would lead to constriction of the membrane tube. A right-handed helix at the inside of a tube would lead to tube expansion. So as we see, Mgm1 motor activity can have multiple outcomes depending on filament assembly and the underlying membrane template.
Published in
Katja Faelber, Lea Dietrich, Jeffrey K. Noel, Florian Wollweber, Anna-Katharina Pfitzner, Alexander Mühleip, Ricardo Sánchez, Misha Kudryashev, Nicolas Chiaruttini, Hauke Lilie, Jeanette Schlegel, Eva Rosenbaum, Manuel Hessenberger, Claudia Matthaeus, Séverine Kunz, Alexander von der Malsburg, Frank Noé, Aurélien Roux, Martin van der Laan, Werner Kühlbrandt and Oliver Daumke (2019). Structure and assembly of the mitochondrial membrane remodelling GTPase Mgm1, Nature, 571(7765), 429-433.
DOI 10.1038/s41586-019-1372-3
Structural coordinates published at 
: 6QL4
: 6QL4
Katja Faelber, Lea Dietrich, Jeffrey K. Noel, Florian Wollweber, Anna-Katharina Pfitzner, Alexander Mühleip, Ricardo Sánchez, Misha Kudryashev, Nicolas Chiaruttini, Hauke Lilie, Jeanette Schlegel, Eva Rosenbaum, Manuel Hessenberger, Claudia Matthaeus, Séverine Kunz, Alexander von der Malsburg, Frank Noé, Aurélien Roux, Martin van der Laan, Werner Kühlbrandt and Oliver Daumke (2019). Structure and assembly of the mitochondrial membrane remodelling GTPase Mgm1, Nature, 571(7765), 429-433.
DOI 10.1038/s41586-019-1372-3
