The essential function of Tim12 in vivo is ensured by the assembly interactions of its C-terminal domain.
The small Tims chaperone hydrophobic precursors across the mitochondrial intermembrane space. Tim9 and Tim10 form the soluble TIM10 complex that binds precursors exiting from the outer membrane. Tim12 functions downstream, as the only small Tim peripherally attached on the inner membrane. We show that Tim12 has an intrinsic affinity for inner mitochondrial membrane lipids, in contrast to the other small Tims. We find that the C-terminal end of Tim12 is essential in vivo. Its deletion crucially abolishes assembly of Tim12 in complexes with the other Tims. The N-terminal end contains targeting information and also mediates direct binding of Tim12 to the transmembrane segments of the carrier substrates. These results provide a molecular basis for the concept that the essential role of Tim12 relies on its unique assembly properties that allow this subunit to bridge the soluble and membrane-embedded translocases in the carrier import pathway.
Lionaki
Eirini
E
Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas, Heraklion 71110, Crete, Greece.
de Marcos Lousa
Carine
C
Baud
Catherine
C
Vougioukalaki
Maria
M
Panayotou
George
G
Tokatlidis
Kostas
K
D000595:Amino Acid Sequence; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes; D029701:Saccharomyces cerevisiae Proteins; C107250:TIM10 protein, S cerevisiae; C100674:TIM12 protein, S cerevisiae; C116366:Tim9 protein, S cerevisiae