Spatiotemporal stop-and-go dynamics of the mitochondrial TOM core complex correlates with channel activity.
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ABSTRACT:
SUBMITTER: Wang S
PROVIDER: S-EPMC9114391 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The translocase of the outer mitochondrial membrane (TOM) complex is the main entry gate for mitochondrial precursor proteins synthesized on cytosolic ribosomes. Here we report the single-particle cryo-electron microscopy (cryo-EM) structure of the dimeric human TOM core complex (TOM-CC). Two Tom40 β-barrel proteins, connected by two Tom22 receptor subunits and one phospholipid, form the protein-conducting channels. The small Tom proteins Tom5, Tom6, and Tom7 surround the channel and have notable configurations. The distinct electrostatic features of the complex, including the pronounced negative interior and the positive regions at the periphery and center of the dimer on the intermembrane space (IMS) side, provide insight into the preprotein translocation mechanism. Further, two dimeric TOM complexes may associate to form tetramer in the shape of a parallelogram, offering a potential explanation into the unusual structural features of Tom subunits and a new perspective of viewing the import of mitochondrial proteins.
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Project description:Nearly all mitochondrial proteins are encoded by the nuclear genome and imported into mitochondria after synthesis on cytosolic ribosomes. These precursor proteins are translocated into mitochondria by the TOM complex, a protein-conducting channel in the mitochondrial outer membrane. We have determined high-resolution cryo-EM structures of the core TOM complex from Saccharomyces cerevisiae in dimeric and tetrameric forms. Dimeric TOM consists of two copies each of five proteins arranged in two-fold symmetry: pore-forming β-barrel protein Tom40 and four auxiliary α-helical transmembrane proteins. The pore of each Tom40 has an overall negatively charged inner surface attributed to multiple functionally important acidic patches. The tetrameric complex is essentially a dimer of dimeric TOM, which may be capable of forming higher-order oligomers. Our study reveals the detailed molecular organization of the TOM complex and provides new insights about the mechanism of protein translocation into mitochondria.
| S-EPMC8439582 | biostudies-literature
Project description:Oxidative phosphorylation (OXPHOS) is essential for the synthesis of the vast majority of ATP in eukaryotic cells. It is carried out by multi-protein assemblies that form the electron transport chain (ETC), which are coupled to the mitochondrial ATP synthase, which uses the proton gradient generated by the ETC to drive ATP synthesis. The assembly of the OXPHOS protein machinery requires the coordinated integration of proteins encoded in the nuclear and the mitochondrial genomes, imposing an additional layer of complexity. While the biogenesis of the individual OXPHOS complexes is well understood, it remains unknown how the assembly of the ETC and ATP synthase is coordinated to achieve the correct stoichiometry of the OXPHOS machinery. Here, we identify the mitochondrial regulatory hub for respiratory assembly (MiRA), which serves as a platform on which complex IV and complex V biogenesis are synchronised to ensure balanced assembly of the ETC and complex V. At the molecular level, this is achieved by a stop-and-go safeguarding mechanism: The novel mitochondrial protein Mra1 binds to and slows down complex IV assembly. Two Go signals are then required for assembly to proceed: Binding of the complex IV assembly factor Rcf2 and interaction with the mitoribosome, which translates the complex V subunit Atp9. Both Go signals induce the clipping and subsequent degradation of Mra1, relieving the molecular brake and allowing parallel maturation of complexes IV and V. The absence of the stop-and-go safety mechanism results in the formation of immature complexes, decreased ATP levels and reduced cell viability. The antagonistic activities at MiRA provide a regulated orchestration of complex IV and V assembly which is essential to avoid the predominance of either complex and an unbalanced ratio of OXPHOS complexes, thus ensuring the correct stoichiometry of protein machineries encoded by two different genomes.
2024-02-16 | PXD044749 | Pride
Project description:Oxidative phosphorylation (OXPHOS) is essential for the synthesis of the vast majority of ATP in eukaryotic cells. It is carried out by multi-protein assemblies that form the electron transport chain (ETC), which are coupled to the mitochondrial ATP synthase, which uses the proton gradient generated by the ETC to drive ATP synthesis. The assembly of the OXPHOS protein machinery requires the coordinated integration of proteins encoded in the nuclear and the mitochondrial genomes, imposing an additional layer of complexity. While the biogenesis of the individual OXPHOS complexes is well understood, it remains unknown how the assembly of the ETC and ATP synthase is coordinated to achieve the correct stoichiometry of the OXPHOS machinery. Here, we identify the mitochondrial regulatory hub for respiratory assembly (MiRA), which serves as a platform on which complex IV and complex V biogenesis are synchronised to ensure balanced assembly of the ETC and complex V. At the molecular level, this is achieved by a stop-and-go safeguarding mechanism: The novel mitochondrial protein Mra1 binds to and slows down complex IV assembly. Two Go signals are then required for assembly to proceed: Binding of the complex IV assembly factor Rcf2 and interaction with the mitoribosome, which translates the complex V subunit Atp9. Both Go signals induce the clipping and subsequent degradation of Mra1, relieving the molecular break and allowing parallel maturation of complexes IV and V. The absence of the stop-and-go safety mechanism results in the formation of immature complexes, decreased ATP levels and reduced cell viability. The antagonistic activities at MiRA provide a regulated orchestration of complex IV and V assembly which is essential to avoid the predominance of either complex and an unbalanced ratio of OXPHOS complexes, thus ensuring the correct stoichiometry of protein machineries encoded by two different genomes.
2024-02-16 | PXD044800 | Pride
Project description:Oxidative phosphorylation (OXPHOS) is essential for the synthesis of the vast majority of ATP in eukaryotic cells. It is carried out by multi-protein assemblies that form the electron transport chain (ETC), which are coupled to the mitochondrial ATP synthase, which uses the proton gradient generated by the ETC to drive ATP synthesis. The assembly of the OXPHOS protein machinery requires the coordinated integration of proteins encoded in the nuclear and the mitochondrial genomes, imposing an additional layer of complexity. While the biogenesis of the individual OXPHOS complexes is well understood, it remains unknown how the assembly of the ETC and ATP synthase is coordinated to achieve the correct stoichiometry of the OXPHOS machinery. Here, we identify the mitochondrial regulatory hub for respiratory assembly (MiRA), which serves as a platform on which complex IV and complex V biogenesis are synchronised to ensure balanced assembly of the ETC and complex V. At the molecular level, this is achieved by a stop-and-go safeguarding mechanism: The novel mitochondrial protein Mra1 binds to and slows down complex IV assembly. Two Go signals are then required for assembly to proceed: Binding of the complex IV assembly factor Rcf2 and interaction with the mitoribosome, which translates the complex V subunit Atp9. Both Go signals induce the clipping and subsequent degradation of Mra1, relieving the molecular brake and allowing parallel maturation of complexes IV and V. The absence of the stop-and-go safety mechanism results in the formation of immature complexes, decreased ATP levels and reduced cell viability. The antagonistic activities at MiRA provide a regulated orchestration of complex IV and V assembly which is essential to avoid the predominance of either complex and an unbalanced ratio of OXPHOS complexes, thus ensuring the correct stoichiometry of protein machineries encoded by two different genomes.
2024-02-16 | PXD044615 | Pride
Project description:The structure of the TOM-complex from Neurospora crassa was characterized using single particle electron microscopy. In order to unambigously identify and characterize the constituting subunits and exclude the presence of previously uncharacterized subunits, the samples were analyzed using proteolytic digests and LC-MS/MS prior to EM structure determination.
2017-08-16 | PXD006827 | Pride
Project description: Not available
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Project description:Contemporary chemoenzymatic approaches can provide highly complex multi-antennary N-linked glycans. These procedures are, however, very demanding and typically involve as many as 100 chemical steps to prepare advanced intermediates that can be diversified by glycosyltransferases in a branch-selective manner to give asymmetrical structures commonly found in nature. Only highly specialized laboratories can perform such syntheses, which greatly hampers progress in glycoscience. Here we describe a biomimetic approach in which a readily available bi-antennary glycopeptide can be converted in ten or fewer chemical and enzymatic steps into multi-antennary N-glycans that at each arm can be uniquely extended by glycosyltransferases to give access to highly complex asymmetrically branched N-glycans. A key feature of our approach is the installation of additional branching points using recombinant MGAT4 and MGAT5 in combination with unnatural sugar donors. At an appropriate point in the enzymatic synthesis, the unnatural monosaccharides can be converted into their natural counterpart, allowing each arm to be elaborated into a unique appendage.
| S-EPMC6347513 | biostudies-literature
Project description:Electrophysiological devices are critical for mapping eloquent and diseased brain regions and for therapeutic neuromodulation in clinical settings and are extensively used for research in brain-machine interfaces. However, the existing clinical and experimental devices are often limited in either spatial resolution or cortical coverage. Here, we developed scalable manufacturing processes with a dense electrical connection scheme to achieve reconfigurable thin-film, multithousand-channel neurophysiological recording grids using platinum nanorods (PtNRGrids). With PtNRGrids, we have achieved a multithousand-channel array of small (30 μm) contacts with low impedance, providing high spatial and temporal resolution over a large cortical area. We demonstrated that PtNRGrids can resolve submillimeter functional organization of the barrel cortex in anesthetized rats that captured the tissue structure. In the clinical setting, PtNRGrids resolved fine, complex temporal dynamics from the cortical surface in an awake human patient performing grasping tasks. In addition, the PtNRGrids identified the spatial spread and dynamics of epileptic discharges in a patient undergoing epilepsy surgery at 1-mm spatial resolution, including activity induced by direct electrical stimulation. Collectively, these findings demonstrated the power of the PtNRGrids to transform clinical mapping and research with brain-machine interfaces.
| S-EPMC9650779 | biostudies-literature
Project description:Precursor proteins of the solute carrier family and of channel forming Tim components are imported into mitochondria in two main steps. First, they are translocated through the TOM complex in the outer membrane, a process assisted by the Tim9/Tim10 complex. They are passed on to the TIM22 complex, which facilitates their insertion into the inner membrane. In the present study, we have analyzed the function of the Tim9/Tim10 complex in the translocation of substrates across the outer membrane of mitochondria. The purified TOM core complex was reconstituted into lipid vesicles in which purified Tim9/Tim10 complex was entrapped. The precursor of the ADP/ATP carrier (AAC) was found to be translocated across the membrane of such lipid vesicles. Thus, these components are sufficient for translocation of AAC precursor across the outer membrane. Peptide libraries covering various substrate proteins were used to identify segments that are bound by Tim9/Tim10 complex upon translocation through the TOM complex. The patterns of binding sites on the substrate proteins suggest a mechanism by which portions of membrane-spanning segments together with flanking hydrophilic segments are recognized and bound by the Tim9/Tim10 complex as they emerge from the TOM complex into the intermembrane space.
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