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J Mol Biol. 2015 Aug 14;427(16):2599-609. doi: 10.1016/j.jmb.2015.03.006. Epub 2015 Mar 14.

Mitochondrial Genome Maintenance 1 (Mgm1) Protein Alters Membrane Topology and Promotes Local Membrane Bending.

Author information

1
Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
2
Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9.
3
Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan.
4
Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9; Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3E5.
5
Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8. Electronic address: angus.mcquibban@utoronto.ca.

Abstract

Large GTPases of the dynamin superfamily promote membrane fusion and division, processes that are crucial for intracellular trafficking and organellar dynamics. To promote membrane scission, dynamin proteins polymerize, wrap around, and constrict the membrane; however, the mechanism underlying their role in membrane fusion remains unclear. We previously reported that the mitochondrial dynamin-related protein mitochondrial genome maintenance 1 (Mgm1) mediates fusion by first tethering opposing membranes and then undergoing a nucleotide-dependent structural transition. However, it is still unclear how Mgm1 directly affects the membrane to drive fusion of tethered membranes. Here, we show that Mgm1 association with the membrane alters the topography of the membrane, promoting local membrane bending. We also demonstrate that Mgm1 creates membrane ruffles resulting in the formation of tubular structures on both supported lipid bilayers and liposomes. These data suggest that Mgm1 membrane interactions impose a mechanical force on the membrane to overcome the hydrophilic repulsion of the phospholipid head groups and initiate the fusion reaction. The work reported here provides new insights into a possible mechanism of Mgm1-driven mitochondrial membrane fusion and sheds light into how members of the dynamin superfamily function as fusion molecules.

KEYWORDS:

dynamin; fluorescence microscopy; membrane fusion; mitochondrial dynamics; phospholipid

PMID:
25784211
DOI:
10.1016/j.jmb.2015.03.006
[Indexed for MEDLINE]

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