Chaperoning through the Mitochondrial Intermembrane Space Nils Wiedemann, Nikolaus Pfanner, Agnieszka Chacinska  Molecular Cell  Volume 21, Issue 2, Pages 145-148 (January 2006) DOI: 10.1016/j.molcel.2006.01.001 Copyright © 2006 Elsevier Inc. Terms and Conditions

Figure 1 Mitochondrial Protein Import and the Tim9-Tim10 Complex Nuclear-encoded mitochondrial precursor proteins are guided through the cytosol by molecular chaperones. After translocation by the general translocase of the outer mitochondrial membrane (TOM complex), the import pathways diverge. Preproteins with amino-terminal presequences are transported by the presequence translocase of the inner membrane (TIM23 complex) and the presequence translocase-associated motor (PAM). Hydrophobic carrier proteins of the inner membrane (IM) are escorted through the intermembrane space (IMS) by the Tim9-Tim10 chaperone complex that contains flexible tentacles for interaction with substrate proteins. The carrier proteins are inserted into the inner membrane by the carrier translocase (TIM22 complex) in a membrane potential (Δψ)-dependent manner (the five stages of carrier import are indicated by red boxes). The Tim9-Tim10 complex also chaperones the precursors of β barrel proteins to the sorting and assembly machinery (SAM complex) of the outer membrane (OM). Molecular Cell 2006 21, 145-148DOI: (10.1016/j.molcel.2006.01.001) Copyright © 2006 Elsevier Inc. Terms and Conditions

Figure 2 Assembly of the Tim9-Tim10 Complex in the Mitochondrial IMS The mitochondrial IMS contains specific machinery for import and assembly (MIA) of small proteins with conserved cysteine motifs. Mia40 binds to the precursors of small IMS proteins via disulfide bonds and promotes their import. The sulfhydryl oxidase Erv1 and Mia40 cooperate to form a protein relay for disulfide formation in the IMS. Small Tim subunits with intramolecular disulfide bonds assemble to the hexameric Tim9-Tim10 complex (or the homologous Tim8-Tim13 complex). Molecular Cell 2006 21, 145-148DOI: (10.1016/j.molcel.2006.01.001) Copyright © 2006 Elsevier Inc. Terms and Conditions