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Mitochondria contain translocases for the transport of precursor proteins across their outer and inner membranes. It has been assumed that the translocases also mediate the sorting of proteins to their submitochondrial destination. Here we show that the mitochondrial outer membrane contains a separate sorting and assembly machinery (SAM) that operates after(More)
The presequence translocase of the inner mitochondrial membrane (TIM23 complex) operates at a central junction of protein import. It accepts preproteins from the outer membrane TOM complex and directs them to inner membrane insertion or, in cooperation with the presequence translocase-associated motor (PAM), to the matrix. Little is known of how the TIM23(More)
Mitochondrial proteins with N-terminal targeting signals are transported across the inner membrane via the presequence translocase, which consists of membrane-integrated channel proteins and the matrix Hsp70 import motor. It has not been known how preproteins are directed to the import channel. We have identified the essential protein Tim50, which exposes(More)
The translocase of the outer membrane (TOM complex) is the central entry gate for nuclear-encoded mitochondrial precursor proteins. All Tom proteins are also encoded by nuclear genes and synthesized as precursors in the cytosol. The channel-forming beta-barrel protein Tom40 is targeted to mitochondria via Tom receptors and inserted into the outer membrane(More)
The intermembrane space (IMS) represents the smallest subcompartment of mitochondria. Nevertheless, it plays important roles in the transport and modification of proteins, lipids, and metal ions and in the regulation and assembly of the respiratory chain complexes. Moreover, it is involved in many redox processes and coordinates key steps in programmed cell(More)
Many mitochondrial proteins are synthesized with N-terminal presequences that are removed by specific peptidases. The N-termini of the mature proteins and thus peptidase cleavage sites have only been determined for a small fraction of mitochondrial proteins and yielded a controversial situation for the cleavage site specificity of the major mitochondrial(More)
Porin, also termed the voltage-dependent anion channel, is the most abundant protein of the mitochondrial outer membrane. The process of import and assembly of the protein is known to be dependent on the surface receptor Tom20, but the requirement for other mitochondrial proteins remains controversial. We have used mitochondria from Neurospora crassa and(More)
The mitochondrial outer membrane contains two integral proteins essential for cell viability, Tom40 of the translocase of the outer membrane (TOM complex) and Sam50 of the sorting and assembly machinery (SAM complex). Here we report the identification of Sam35, the first peripheral mitochondrial outer membrane protein that is essential for cell viability.(More)
The biogenesis of mitochondria requires the import of a large number of proteins from the cytosol [1, 2]. Although numerous studies have defined the proteinaceous machineries that mediate mitochondrial protein sorting, little is known about the role of lipids in mitochondrial protein import. Cardiolipin, the signature phospholipid of the mitochondrial inner(More)
Mitochondria are found in all eukaryotic cells and derive from a bacterial endosymbiont [1, 2]. The evolution of a protein import system was a prerequisite for the conversion of the endosymbiont into a true organelle. Tom40, the essential component of the protein translocase of the outer membrane, is conserved in mitochondria of almost all eukaryotes but(More)