Potential membrane remodelling by Mgm1
Potential membrane remodelling by Mgm1
Katja Faelber, Jeffrey Noel and Oliver Daumke - Max Delbrück Center for Molecular Medicine (MDC), Berlin (https://www.mdc-berlin.de/daumke)
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.
Reference:
Faelber et al. (2019): Structure and assembly of the mitochondrial membrane remodelling GTPase Mgm1. Nature, 571(7765):429-433.
Links:
https://doi.org/10.1038/s41586-019-13...
https://www.nature.com/articles/s4158...
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/3...
PDB entry 6QL4 (https://www.rcsb.org/structure/6QL4)
Related Video:
Membrane constriction by Dynamin ( • Membrane constriction by Dynamin )
Molecular Animation by Erik Werner, RNS Berlin
further information at http://www.rns.berlin