ORCID Profile
0000-0001-7873-0722
Current Organisation
Xiangya Hospital Central South University
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Publisher: Elsevier BV
Date: 08-2013
DOI: 10.1016/J.CELL.2013.06.033
Abstract: The mitochondrial outer membrane harbors two protein translocases that are essential for cell viability: the translocase of the outer mitochondrial membrane (TOM) and the sorting and assembly machinery (SAM). The precursors of β-barrel proteins use both translocases-TOM for import to the intermembrane space and SAM for export into the outer membrane. It is unknown if the translocases cooperate and where the β-barrel of newly imported proteins is formed. We established a position-specific assay for monitoring β-barrel formation in vivo and in organello and demonstrated that the β-barrel was formed and membrane inserted while the precursor was bound to SAM. β-barrel formation was inhibited by SAM mutants and, unexpectedly, by mutants of the central import receptor, Tom22. We show that the cytosolic domain of Tom22 links TOM and SAM into a supercomplex, facilitating precursor transfer on the intermembrane space side. Our study reveals receptor-mediated coupling of import and export translocases as a means of precursor channeling.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 25-09-2015
Abstract: Mitochondria, the powerhouses of the cell, are mainly composed of proteins made in the cytosol. These newly synthesized proteins need to be imported across the organelle's membrane through dedicated protein import machinery. Shiota et al. have worked out the architecture and mechanism of the mitochondrial protein import channel. Science , this issue p. 1544
Publisher: American Society for Cell Biology (ASCB)
Date: 15-08-2011
Abstract: The mitochondrial outer membrane contains proteinaceous machineries for the translocation of precursor proteins. The sorting and assembly machinery (SAM) is required for the insertion of β‑barrel proteins into the outer membrane. Sam50 is the channel-forming core subunit of the SAM complex and belongs to the BamA/Sam50/Toc75 family of proteins that have been conserved from Gram-negative bacteria to mitochondria and chloroplasts. These proteins contain one or more N-terminal polypeptide transport-associated (POTRA) domains. POTRA domains can bind precursor proteins, however, different views exist on the role of POTRA domains in the biogenesis of β-barrel proteins. It has been suggested that the single POTRA domain of mitochondrial Sam50 plays a receptor-like function at the SAM complex. We established a system to monitor the interaction of chemical amounts of β-barrel precursor proteins with the SAM complex of wild-type and mutant yeast in organello. We report that the SAM complex lacking the POTRA domain of Sam50 efficiently binds β-barrel precursors, but is impaired in the release of the precursors. These results indicate the POTRA domain of Sam50 is not essential for recognition of β-barrel precursors but functions in a subsequent step to promote the release of precursor proteins from the SAM complex.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-01-2018
Abstract: The mechanism of membrane insertion and assembly of b-barrel proteins is a central question of outer membrane biogenesis of mitochondria, chloroplasts, and Gram-negative bacteria. Höhr et al. developed assays to address this fundamental problem. They systematically mapped precursor proteins transported by the mitochondrial Omp85 channel (Sam50) to elucidate the entire membrane insertion pathway of a precursor in the native membrane environment. Their findings directly demonstrate translocation of precursor proteins through the lumen of the mitochondrial Omp85 channel, signal recognition by β-strand exchange between channel and precursor, and exit through the lateral gate into the membrane. Science , this issue p. eaah6834
No related grants have been discovered for Jian Qiu.