The yeast dynamin-like protein, Mgm1p, functions on the mitochondrial outer membrane to mediate mitochondrial inheritance

The mdm17 mutation causes temperature-dependent defects in mitochondrial in heritance, mitochondrial morphology, and the maintenance of mitochondrial D NA in the yeast Saccharomyces cerevisiae. Defects in mitochondrial transmis sion to daughter buds and changes in mitochondrial morphology were apparent within 30 min after shifting cells to 37 degrees C, while loss of the mito chondrial genome occurred after 4-24 h at the elevated temperature. The mdm 17 lesion mapped to MGM1, a gene encoding a dynamin-like GTPase previously implicated in mitochondrial genome maintenance, and the cloned MGM1 gene co mplements all of the mdm17 mutant phenotypes. Cells with an mgm1-null mutat ion displayed aberrant mitochondrial inheritance and morphology. A version of mgm1 mutated in a conserved residue in the putative GTP-binding site was unable to complement any of the mutant defects. It also caused aberrant mi tochondrial distribution and morphology when expressed at high levels in ce lls that also contained a wild-type copy of the gene. Mgm1p was localized t o the mitochondrial outer membrane and fractionated as a component of a hig h molecular weight complex, These results indicate that Mgm1p is a mitochon drial inheritance and morphology component that functions on the mitochondr ial surface.