Reference: Rujiviphat J, et al. (2009) Phospholipid association is essential for dynamin-related protein Mgm1 to function in mitochondrial membrane fusion. J Biol Chem 284(42):28682-6

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Abstract

Mgm1, the yeast ortholog of mammalian OPA1, is a key component in mitochondrial membrane fusion and is required for maintaining mitochondrial dynamics and morphology. We recently showed that the purified short isoform of Mgm1 (s-Mgm1) possesses GTPase activity, self-assembles into low-order oligomers, and interacts specifically with negatively charged phospholipids. Here, we demonstrate that s-Mgm1 binds to a mixture of phospholipids characteristic of the mitochondrial inner membrane. Binding to physiologically representative lipids results in ~50-fold stimulation of s-Mgm1 GTPase activity. s-Mgm1 point mutants that are defective in oligomerization and lipid-binding do not exhibit such stimulation and do not function in vivo. Electron microscopy and lipid turbidity assays demonstrate that s-Mgm1 promotes liposome interaction. Further, s-Mgm1 assembles onto liposomes as oligomeric rings with 3-fold symmetry. The projection map of negatively stained s-Mgm1 shows six monomers, consistent with two stacked trimers. Taken together, our data identify a lipid-binding domain in Mgm1 and the structural analysis suggests a model of how Mgm1 promotes the fusion of opposing mitochondrial inner membranes.

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Journal Article
Authors
Rujiviphat J, Meglei G, Rubinstein JL, McQuibban GA
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