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Mmm1p, a mitochondrial outer membrane protein, is connected to mitochondrial DNA (mtDNA) nucleoids and required for

A E Hobbs1, M Srinivasan, J M McCaffery

  • 1Department of Cell Biology and Anatomy, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

The Journal of Cell Biology
|March 27, 2001
PubMed

Insights

Mmm1p protein in yeast is crucial for maintaining mitochondrial shape and function. It anchors mitochondrial DNA nucleoids, ensuring proper inheritance and inner membrane structure.

Area of Science:

  • Cell Biology
  • Mitochondrial Biology
  • Molecular Genetics

Background:

  • Mitochondria in yeast (Saccharomyces cerevisiae) form a complex, branched tubular network.
  • The Mmm1p protein is essential for maintaining normal mitochondrial morphology.
  • Mmm1 mutants exhibit spherical mitochondria, indicating a role for Mmm1p in shape regulation.

Purpose of the Study:

  • To investigate the precise function of Mmm1p in yeast mitochondria.
  • To determine the localization of Mmm1p within the cell.
  • To elucidate Mmm1p's role in mitochondrial DNA (mtDNA) maintenance and inheritance.

Main Methods:

  • Utilized a Mmm1p-green fluorescent protein (GFP) fusion to track protein localization in living yeast cells.
  • Observed mitochondrial morphology and mtDNA nucleoid structure in wild-type and mmm1 mutant strains.
  • Examined mtDNA transmission to daughter cells under restrictive temperature conditions.

Main Results:

  • Mmm1p-GFP localizes to punctate structures on the mitochondrial outer membrane, near mtDNA nucleoids.
  • The mmm1-1 mutant shows defects in mtDNA transmission and nucleoid structure collapse at restrictive temperatures.
  • Mmm1p disruption leads to significant disorganization of the mitochondrial inner membrane.

Conclusions:

  • Mmm1p is proposed to link the mitochondrial outer and inner membranes.
  • This linkage is critical for anchoring matrix-localized mtDNA nucleoids.
  • Mmm1p plays a vital role in maintaining mitochondrial shape, mtDNA stability, and inheritance.

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