title: The Tim9p-Tim10p complex binds to the transmembrane domains of the ADP/ATP carrier.
abstract: The soluble Tim9p-Tim10p (Tim, translocase of inner membrane) complex of the mitochondrial intermembrane space mediates the import of the carrier proteins and is a component of the TIM22 import system. The mechanism by which the Tim9p-Tim10p complex assembles and binds the carriers is not well understood, but previous studies have proposed that the conserved cysteine residues in the 'twin CX3C' motif coordinate zinc and potentially generate a zinc-finger-like structure that binds to the matrix loops of the carrier proteins. Here we have purified the native and recombinant Tim9p-Tim10p complex, and show that both complexes resemble each other and consist of three Tim9p and three Tim10p. Results from inductively coupled plasma--mass spectrometry studies failed to detect zinc in the Tim9p-Tim10p complex. Instead, the cysteine residues seemingly formed disulfide linkages. The Tim9p-Tim10p complex bound specifically to the transmembrane domains of the ADP/ATP carrier, but had no affinity for Tim23p, an inner membrane protein that is inserted via the TIM22 complex. The chaperone-like Tim9p-Tim10p complex thus may prevent aggregation of the unfolded carrier proteins in the aqueous intermembrane space.
authors.affiliation: Department of Chemistry and Biochemistry and the Molecular Biology Institute, Box 951569, UCLA, Los Angeles, CA 90095-1569, USA.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Curran
authors.forename: Danielle
authors.initials: D
authors.lastname: Leuenberger
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Oppliger
authors.forename: Carla M
authors.initials: CM
authors.lastname: Koehler
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D003553:Cystine / Q000032:analysis; D007425:Intracellular Membranes / Q000378:metabolism; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000737:chemistry / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000302:isolation & purification / Q000378:metabolism*; D015032:Zinc / Q000032:analysis; D016335:Zinc Fingers
chemical_list: D002352:Carrier Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C107250:TIM10 protein, S cerevisiae; C102549:TIM22 protein, S cerevisiae; C083081:TIM23 protein, S cerevisiae; C116366:Tim9 protein, S cerevisiae; D003553:Cystine; D000226:Mitochondrial ADP, ATP Translocases; D015032:Zinc