title: Human deafness dystonia syndrome is caused by a defect in assembly of the DDP1/TIMM8a-TIMM13 complex.
abstract: Mohr-Tranebjaerg syndrome (MTS/DFN-1) or deafness/dystonia syndrome results from a mutation in deafness/dystonia protein 1/translocase of mitochondrial inner membrane 8a (DDP1/TIMM8a). DDP1/TIMM8a is similar to a family of yeast proteins in the mitochondrial intermembrane space which mediate the import and insertion of inner membrane proteins. We now show that TIMM8a assembles in a 70 kDa complex in the intermembrane space with TIMM13. DDP1/TIMM8a is not detectable in fibroblasts derived from a patient with a missense mutation in the DDP1/TIMM8a gene; the point mutation results in cysteine-66 being changed to tryptophan-66 in the conserved 'twin CX(3)C' motif. The corresponding mutation in yeast translocase of inner membrane 8p (Tim8p) yields an unstable protein that does not assemble with yeast Tim13p. DDP1/TIMM8a, when expressed with TIMM13 in yeast mitochondria lacking the Tim8p-Tim13p complex, restores Tim23p import, and TIMM8a and TIMM13 can be cross-linked to the hTim23 import intermediate in rat and yeast mitochondria. In a similar manner to Tim8p, TIMM8a seemingly mediates the import of hTim23. Deafness/dystonia syndrome thus may be caused by decreased levels of Tim23 in the mitochondrial inner membrane in affected tissues.
authors.affiliation: Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095-1569, USA.
authors.forename: Karin
authors.initials: K
authors.lastname: Roesch
authors.forename: Sean P
authors.initials: SP
authors.lastname: Curran
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Tranebjaerg
authors.forename: Carla M
authors.initials: CM
authors.lastname: Koehler
mesh_terms: D019943:Amino Acid Substitution; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics*; D003638:Deafness / Q000235:genetics*; D004421:Dystonia / Q000235:genetics*; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000378:metabolism; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008970:Molecular Weight; D020125:Mutation, Missense; D017354:Point Mutation; D013577:Syndrome; D014364:Tryptophan / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D026901:Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; C118122:TIMM8A protein, human; D014364:Tryptophan