| Description |
Mitochondria are semiautonomous organelles essential for eukaryotic life. Mitochondria house the machinery required for cellular respiration and energy production, and hundreds of enzymes required for essential biochemical pathways. Mitochondrial number and distribution are regulated by coordinated mitochondrial fission, fusion, and movement events, and must continually adapt to meet the changing spatial and temporal energy requirements of growing cells. In recent years, it has become clear that defects in mitochondrial fission, fusion, or movement can lead to cellular dysfunction and disease. This dissertation investigates the molecular basis for the process of mitochondrial fission in the budding yeast, Saccharomyces cerevisiae . Mitochondrial fission is mediated by macromolecular protein complexes localized to the cytoplasmic face of the outer mitochondrial membrane. These complexes are composed of at least three components, Dnm1p, Fis1p, and Mdv1p. Studies presented in this dissertation investigate the coordinated series of inter- and intramolecular interactions required to recruit and assemble these three proteins into functional fission complexes. Studies detailed in Chapter 2 suggest that the cytoplasmic domain of Fis1p interacts directly with Mdv1p, and that this interaction is required for the recruitment of Dnm1p to functional fission complexes. Results presented in Chapter 3 demonstrate that dimeric Dnm1p is initially recruited to mitochondria, and that higher-ordered Dnm1p oligomerization occurs after mitochondrial recruitment. In addition, Chapter 3 suggests that GTP hydrolysis by Dnm1p is required to destabilize mitochondrial fission complexes after fission occurs. Analyses presented in Chapter 4 characterize the domain of Dnm1p required for Dnm1p association with the actin cytoskeleton. Together, these studies comprise a significant advance in our understanding of the molecular basis for mitochondrial fission, and raise important issues for future study. |
