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

Shepard KA, Yaffe MP - J. Cell Biol. (1999)

Bottom Line: It also caused aberrant mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene.Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex.These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of California, San Diego, La Jolla, California 92093-0347, USA.

ABSTRACT
The mdm17 mutation causes temperature-dependent defects in mitochondrial inheritance, mitochondrial morphology, and the maintenance of mitochondrial DNA in the yeast Saccharomyces cerevisiae. Defects in mitochondrial transmission to daughter buds and changes in mitochondrial morphology were apparent within 30 min after shifting cells to 37 degrees C, while loss of the mitochondrial genome occurred after 4-24 h at the elevated temperature. The mdm17 lesion mapped to MGM1, a gene encoding a dynamin-like GTPase previously implicated in mitochondrial genome maintenance, and the cloned MGM1 gene complements all of the mdm17 mutant phenotypes. Cells with an mgm1- mutation 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 mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene. Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex. These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

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Mgm1p participates in  a high molecular mass complex.  Purified mitochondria were solubilized in 1% Triton X-100 and  the mixture was centrifuged to  remove insoluble debris. The supernatant was loaded onto a  Sephacryl-300 column and subjected to gel filtration chromatography. Proteins in collected  fractions were precipitated with  TCA and analyzed by SDS-PAGE and immunoblotting.  The percentage of total Mgm1p  recovered was plotted for each  fraction. Arrows indicate peak  fractions for marker proteins:  669 kD, thyroglobulin; 443 kD,  apoferritin; 150 kD, carbonic anhydrase; and 86 kD, bovine serum albumin. Also shown are  elution peak fractions for two other outer membrane proteins, OM45 and Tom70p. The latter protein was reported to be in a complex  with Tom37p (Mas37p) with an apparent molecular mass of ∼110 kD (Gratzer et al., 1995).
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Figure 6: Mgm1p participates in a high molecular mass complex. Purified mitochondria were solubilized in 1% Triton X-100 and the mixture was centrifuged to remove insoluble debris. The supernatant was loaded onto a Sephacryl-300 column and subjected to gel filtration chromatography. Proteins in collected fractions were precipitated with TCA and analyzed by SDS-PAGE and immunoblotting. The percentage of total Mgm1p recovered was plotted for each fraction. Arrows indicate peak fractions for marker proteins: 669 kD, thyroglobulin; 443 kD, apoferritin; 150 kD, carbonic anhydrase; and 86 kD, bovine serum albumin. Also shown are elution peak fractions for two other outer membrane proteins, OM45 and Tom70p. The latter protein was reported to be in a complex with Tom37p (Mas37p) with an apparent molecular mass of ∼110 kD (Gratzer et al., 1995).

Mentions: The state of Mgm1p in the mitochondrial outer membrane was further characterized by gel filtration analysis of mitochondrial proteins solubilized in 1% Triton X-100. About 60% of Mgm1p eluted in a peak corresponding to a molecular mass of ∼400 kD, while the remainder of the protein eluted in a peak appropriate to the monomeric size (90–100 kD) (Fig. 6). The 90-kD (fragment) form of the protein eluted in a distinct peak with an apparent molecular mass of ∼120 kD (data not shown). The elution behavior of Mgm1p was distinct from that of two other integral proteins of the mitochondrial outer membrane, Tom70p and OM45 (Fig. 6). These results suggest that Mgm1p is part of a high molecular mass complex either in a homo-oligomeric state or complexed with other proteins on the mitochondrial surface.


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

Shepard KA, Yaffe MP - J. Cell Biol. (1999)

Mgm1p participates in  a high molecular mass complex.  Purified mitochondria were solubilized in 1% Triton X-100 and  the mixture was centrifuged to  remove insoluble debris. The supernatant was loaded onto a  Sephacryl-300 column and subjected to gel filtration chromatography. Proteins in collected  fractions were precipitated with  TCA and analyzed by SDS-PAGE and immunoblotting.  The percentage of total Mgm1p  recovered was plotted for each  fraction. Arrows indicate peak  fractions for marker proteins:  669 kD, thyroglobulin; 443 kD,  apoferritin; 150 kD, carbonic anhydrase; and 86 kD, bovine serum albumin. Also shown are  elution peak fractions for two other outer membrane proteins, OM45 and Tom70p. The latter protein was reported to be in a complex  with Tom37p (Mas37p) with an apparent molecular mass of ∼110 kD (Gratzer et al., 1995).
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Related In: Results  -  Collection

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Figure 6: Mgm1p participates in a high molecular mass complex. Purified mitochondria were solubilized in 1% Triton X-100 and the mixture was centrifuged to remove insoluble debris. The supernatant was loaded onto a Sephacryl-300 column and subjected to gel filtration chromatography. Proteins in collected fractions were precipitated with TCA and analyzed by SDS-PAGE and immunoblotting. The percentage of total Mgm1p recovered was plotted for each fraction. Arrows indicate peak fractions for marker proteins: 669 kD, thyroglobulin; 443 kD, apoferritin; 150 kD, carbonic anhydrase; and 86 kD, bovine serum albumin. Also shown are elution peak fractions for two other outer membrane proteins, OM45 and Tom70p. The latter protein was reported to be in a complex with Tom37p (Mas37p) with an apparent molecular mass of ∼110 kD (Gratzer et al., 1995).
Mentions: The state of Mgm1p in the mitochondrial outer membrane was further characterized by gel filtration analysis of mitochondrial proteins solubilized in 1% Triton X-100. About 60% of Mgm1p eluted in a peak corresponding to a molecular mass of ∼400 kD, while the remainder of the protein eluted in a peak appropriate to the monomeric size (90–100 kD) (Fig. 6). The 90-kD (fragment) form of the protein eluted in a distinct peak with an apparent molecular mass of ∼120 kD (data not shown). The elution behavior of Mgm1p was distinct from that of two other integral proteins of the mitochondrial outer membrane, Tom70p and OM45 (Fig. 6). These results suggest that Mgm1p is part of a high molecular mass complex either in a homo-oligomeric state or complexed with other proteins on the mitochondrial surface.

Bottom Line: It also caused aberrant mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene.Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex.These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of California, San Diego, La Jolla, California 92093-0347, USA.

ABSTRACT
The mdm17 mutation causes temperature-dependent defects in mitochondrial inheritance, mitochondrial morphology, and the maintenance of mitochondrial DNA in the yeast Saccharomyces cerevisiae. Defects in mitochondrial transmission to daughter buds and changes in mitochondrial morphology were apparent within 30 min after shifting cells to 37 degrees C, while loss of the mitochondrial genome occurred after 4-24 h at the elevated temperature. The mdm17 lesion mapped to MGM1, a gene encoding a dynamin-like GTPase previously implicated in mitochondrial genome maintenance, and the cloned MGM1 gene complements all of the mdm17 mutant phenotypes. Cells with an mgm1- mutation 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 mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene. Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex. These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

Show MeSH
Related in: MedlinePlus