Mmm1p, a Mitochondrial Outer Membrane Protein, Is Connected to Mitochondrial DNA (mtDNA) Nucleoids and Required for mtDNA Stability

• Published in: The Journal of cell biology Vol. 152; no. 2; pp. 401 - 410
• Main Authors: Alyson E. Aiken Hobbs, Srinivasan, Maithreyan, McCaffery, J. Michael, Jensen, Robert E.
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 22.01.2001; The Rockefeller University Press
• Subjects: Actins; Actins - metabolism; Cells; Daughter cells; Deoxyribonucleic acid; DNA; DNA, Mitochondrial - chemistry; DNA, Mitochondrial - metabolism; Fluorescence; Fungal Proteins - analysis; Fungal Proteins - genetics; Fungal Proteins - metabolism; Genotype; Green Fluorescent Proteins; Intracellular Membranes - physiology; Intracellular Membranes - ultrastructure; Kinetics; Luminescent Proteins - analysis; Luminescent Proteins - genetics; Membrane proteins; Membrane Proteins - analysis; Membrane Proteins - genetics; Membrane Proteins - metabolism; Membranes; Microscopy, Electron; Microscopy, Immunoelectron; Mitochondria; Mitochondria - physiology; Mitochondria - ultrastructure; Mitochondrial DNA; mmm1 gene; Mmm1 protein; Mother cells; Organelles - physiology; Organelles - ultrastructure; Original; P branes; Proteins; Recombinant Fusion Proteins - analysis; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - physiology; Saccharomyces cerevisiae - ultrastructure; Saccharomyces cerevisiae Proteins; Yeast; Yeasts
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.152.2.401

In the yeast Saccharomyces cerevisiae, mitochondria form a branched, tubular reticulum in the periphery of the cell. Mmm1p is required to maintain normal mitochondrial shape and in mmm1 mutants mitochondria form large, spherical organelles. To further explore Mmm1p function, we examined the localization of a Mmm1p-green fluorescent protein (GFP) fusion in living cells. We found that Mmm1p-GFP is located in small, punctate structures on the mitochondrial outer membrane, adjacent to a subset of matrix-localized mitochondrial DNA nucleoids. We also found that the temperature-sensitive mmm1-1 mutant was defective in transmission of mitochondrial DNA to daughter cells immediately after the shift to restrictive temperature. Normal mitochondrial nucleoid structure also collapsed at the nonpermissive temperature with similar kinetics. Moreover, we found that mitochondrial inner membrane structure is dramatically disorganized in mmm1 disruption strains. We propose that Mmm1p is part of a connection between the mitochondrial outer and inner membranes, anchoring mitochondrial DNA nucleoids in the matrix.