MOM22 is a receptor for mitochondrial targeting sequences and cooperates with MOM19.

Mayer, Andreas; Nargang, Frank E.; Neupert, Walter; Lill, Roland

doi:10.1002/j.1460-2075.1995.tb00094.x

Cited by 133 publications

(114 citation statements)

References 41 publications

(57 reference statements)

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“…As controls, AD-Tom20 interacted with BD-Tom22, and vice versa (Fig. 6E), confirming a genetic as well as physical interaction of Tom20 and Tom22 (38,39). The import sequence fused to BD (BD-N) interacted with both the cytoplasmic segment of Tom20 and Tom22, which were fused to AD (AD-20 and AD-22, respectively), suggesting that the import signal was recognized by Tom20 and Tom22 in the initial import processes.…”

Section: Figsupporting

confidence: 56%

Targeting and Assembly of Rat Mitochondrial Translocase of Outer Membrane 22 (TOM22) into the TOM Complex

Nakamura

Suzuki

Sakaguchi

et al. 2004

Journal of Biological Chemistry

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Tom22 is a preprotein receptor and organizer of the mitochondrial outer membrane translocase complex (TOM complex). Rat Tom22 (rTOM22) is a 142-residue protein, embedded in the outer membrane through the internal transmembrane domain (TMD) with 82 N-terminal residues in the cytosol and 41 C-terminal residues in the intermembrane space. We analyzed the signals that target rTOM22 to the mitochondrial outer membrane and assembly into the TOM complex in cultured mammalian cells. Deletions or mutations were systematically introduced into the molecule, and the intracellular localization of the mutant constructs in HeLa cells was examined by confocal microscopy and cell fractionation. Their assembly into the TOM complex was also examined using blue native gel electrophoresis. These experiments revealed three separate structural elements: a cytoplasmic 10-residue segment with an acidic ␣-helical structure located 30 residues upstream of the TMD (the import sequence), TMD with an appropriate hydrophobicity, and a 20-residue C-terminal segment located 22 residues downstream of the TMD (C-tail signal). The import sequence and TMD were both essential for targeting and integration into the TOM complex, whereas the C-tail signal affected the import efficiency. The import sequence combined with foreign TMD functioned as a mitochondrial targeting and anchor signal but failed to integrate the construct into the TOM complex. Thus, the mitochondrial-targeting and TOM integration signal could be discriminated. A yeast two-hybrid assay revealed that the import sequence interacted with two intramolecular elements, the TMD and C-tail signal, and that it also interacted with the import receptor Tom20.

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Section: Figsupporting

confidence: 56%

Targeting and Assembly of Rat Mitochondrial Translocase of Outer Membrane 22 (TOM22) into the TOM Complex

Nakamura

Suzuki

Sakaguchi

et al. 2004

Journal of Biological Chemistry

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“…These components of the TOM complex have been shown to recognize the N-terminal mitochondrial presequences of matrix-targeted preproteins [33]. The absence of the N-terminal segment results in a decreased import efficiency.…”

Section: A269-283porinmentioning

confidence: 99%

Role of the N‐ and C‐termini of porin in import into the outer membrane of Neurospora mitochondria

et al. 1996

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The signals for targeting and assembly of porin, a protein of the mitochondrial outer membrane, have not been clearly defined. Targeting information has been hypothesized to be contained in the N-terminus, which may form an amphipathic a-helix, and in the C-terminal portion of the protein. Here, the role of the extreme N-and C-termini of porin from Neurospora crassa in its import into the mitochondrial outer membrane was investigated. Deletion mutants were constructed which lacked the N-terminal 12 or 20 residues or the C-terminal 15 residues. The porins truncated at their N-termini were imported in a receptordependent manner into the outer membrane of isolated mitochondria. When integrated into the outer membrane, these preproteins displayed an increased sensitivity to protease as compared to wild-type porin. In contrast, mutant porin truncated at its C-terminus did not acquire protease resistance upon incubation with mitochondria. Thus, unlike most other mitochondrial preproteins, porin appears to contain important targeting and/or assembly information at its C-terminus, rather than at the N-terminus.

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“…The TOM complex contains components that expose domains to the cytosol and function as preprotein receptors. The major receptor is Tom20, which is involved, together with Tom22, in the translocation of most precursors (5)(6)(7). Another receptor that forms a binding site for a more restricted set of preproteins, most notably the mitochondrial carrier family, is Tom70 (8,9).…”

mentioning

confidence: 99%

Assembly of Tom6 and Tom7 into the TOM Core Complex ofNeurospora crassa

Dembowski

Künkele

Nargang

et al. 2001

Journal of Biological Chemistry

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Translocation of preproteins across the mitochondrial outer membrane is mediated by the translocase of the outer mitochondrial membrane (TOM) complex. We report the molecular identification of Tom6 and Tom7, two small subunits of the TOM core complex in the fungus Neurospora crassa. Cross-linking experiments showed that both proteins were found to be in direct contact with the major component of the pore, Tom40. In addition, Tom6 was observed to interact with Tom22 in a manner that depends on the presence of preproteins in transit. Precursors of both proteins are able to insert into the outer membrane in vitro and are assembled into authentic TOM complexes. The insertion pathway of these proteins shares a common binding site with the general import pathway as the assembly of both Tom6 and Tom7 was competed by a matrix-destined precursor protein. This assembly was dependent on the integrity of receptor components of the TOM machinery and is highly specific as in vitro-synthesized yeast Tom6 was not assembled into N. crassa TOM complex. The targeting and assembly information within the Tom6 sequence was found to be located in the transmembrane segment and a flanking segment toward the N-terminal, cytosolic side. A hybrid protein composed of the C-terminal domain of yeast Tom6 and the cytosolic domain of N. crassa Tom6 was targeted to the mitochondria but was not taken up into TOM complexes. Thus, both segments are required for assembly into the TOM complex. A model for the topogenesis of the small Tom subunits is discussed.

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MOM22 is a receptor for mitochondrial targeting sequences and cooperates with MOM19.

Cited by 133 publications

References 41 publications

Targeting and Assembly of Rat Mitochondrial Translocase of Outer Membrane 22 (TOM22) into the TOM Complex

Targeting and Assembly of Rat Mitochondrial Translocase of Outer Membrane 22 (TOM22) into the TOM Complex

Role of the N‐ and C‐termini of porin in import into the outer membrane of Neurospora mitochondria

Assembly of Tom6 and Tom7 into the TOM Core Complex ofNeurospora crassa

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