title: Ugo1p links the Fzo1p and Mgm1p GTPases for mitochondrial fusion.
abstract: In yeast, mitochondrial fusion requires Ugo1p and two GTPases, Fzo1p and Mgm1p. Ugo1p is anchored in the mitochondrial outer membrane with its N terminus facing the cytosol and C terminus in the intermembrane space. Fzo1p is also an outer membrane protein, whereas Mgm1p is located in the intermembrane space. Recent studies suggest that these three proteins form protein complexes that mediate mitochondrial fusion. Here, we show that the cytoplasmic domain of Ugo1p directly interacts with Fzo1p, whereas its intermembrane space domain binds to Mgm1p. We identified the Ugo1p-binding site in Fzo1p and demonstrated that Ugo1p-Fzo1p interaction is essential for the formation of mitochondrial shape, maintenance of mitochondrial DNA, and fusion of mitochondria. Although the GTPase domains of Fzo1p and Mgm1p regulate mitochondrial fusion, they were not required for association with Ugo1p. Furthermore, we found that Ugo1p bridges the interaction between Fzo1p and Mgm1p in mitochondria. Our data indicate that distinct regions of Ugo1p bind directly to Fzo1p and Mgm1p and thereby link these two GTPases during mitochondrial fusion.
authors.affiliation: Department of Cell Biology, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA. hesaki@jhmi.edu
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sesaki
authors.forename: Robert E
authors.initials: RE
authors.lastname: Jensen
mesh_terms: D001665:Binding Sites; D003593:Cytoplasm / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology*
chemical_list: D004272:DNA, Mitochondrial; C082883:MGM1 protein, S cerevisiae; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; C423986:UGO1 protein, S cerevisiae; C401395:FZO1 protein, S cerevisiae; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins