title: The C-terminal domain of Fcj1 is required for formation of crista junctions and interacts with the TOB/SAM complex in mitochondria.
abstract: Crista junctions (CJs) are tubular invaginations of the inner membrane of mitochondria that connect the inner boundary with the cristae membrane. These architectural elements are critical for mitochondrial function. The yeast inner membrane protein Fcj1, called mitofilin in mammals, was reported to be preferentially located at CJs and crucial for their formation. Here we investigate the functional roles of individual domains of Fcj1. The most conserved part of Fcj1, the C-terminal domain, is essential for Fcj1 function. In its absence, formation of CJ is strongly impaired and irregular, and stacked cristae are present. This domain interacts with full-length Fcj1, suggesting a role in oligomer formation. It also interacts with Tob55 of the translocase of outer membrane β-barrel proteins (TOB)/sorting and assembly machinery (SAM) complex, which is required for the insertion of β-barrel proteins into the outer membrane. The association of the TOB/SAM complex with contact sites depends on the presence of Fcj1. The biogenesis of β-barrel proteins is not significantly affected in the absence of Fcj1. However, down-regulation of the TOB/SAM complex leads to altered cristae morphology and a moderate reduction in the number of CJs. We propose that the C-terminal domain of Fcj1 is critical for the interaction of Fcj1 with the TOB/SAM complex and thereby for stabilizing CJs in close proximity to the outer membrane. These results assign novel functions to both the C-terminal domain of Fcj1 and the TOB/SAM complex.
authors.affiliation: Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians-Universität, and Center for Integrated Protein Science München, 81377 München, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Körner
authors.forename: Miguel
authors.initials: M
authors.lastname: Barrera
authors.forename: Jovana
authors.initials: J
authors.lastname: Dukanovic
authors.forename: Katharina
authors.initials: K
authors.lastname: Eydt
authors.forename: Max
authors.initials: M
authors.lastname: Harner
authors.forename: Regina
authors.initials: R
authors.lastname: Rabl
authors.forename: Frank
authors.initials: F
authors.lastname: Vogel
authors.forename: Doron
authors.initials: D
authors.lastname: Rapaport
authors.forename: Walter
authors.initials: W
authors.lastname: Neupert
authors.forename: Andreas S
authors.initials: AS
authors.lastname: Reichert
mesh_terms: D017124:Conserved Sequence; D015536:Down-Regulation; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: C542160:Fcj1 protein, S cerevisiae; D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes; D029701:Saccharomyces cerevisiae Proteins