| 1. |
- Bareth, Bettina, et al.
(författare)
-
Oms1 associates with cytochrome c oxidase assembly intermediates to stabilize newly synthesized Cox1
- 2016
-
Ingår i: Molecular Biology of the Cell. - 1059-1524 .- 1939-4586. ; 27:10, s. 1570-1580
-
Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial cytochrome c oxidase assembles in the inner membrane from subunits of dual genetic origin. The assembly process of the enzyme is initiated by membrane insertion of the mitochondria-encoded Cox1 subunit. During complex maturation, transient assembly intermediates, consisting of structural subunits and specialized chaperone-like assembly factors, are formed. In addition, cofactors such as heme and copper have to be inserted into the nascent complex. To regulate the assembly process, the availability of Cox1 is under control of a regulatory feedback cycle in which translation of COX1 mRNA is stalled when assembly intermediates of Cox1 accumulate through inactivation of the translational activator Mss51. Here we isolate a cytochrome c oxidase assembly intermediate in preparatory scale from coa1 Delta. mutant cells, using Mss51 as bait. We demonstrate that at this stage of assembly, the complex has not yet incorporated the heme a cofactors. Using quantitative mass spectrometry, we define the protein composition of the assembly intermediate and unexpectedly identify the putative methyltransferase Oms1 as a constituent. Our analyses show that Oms1 participates in cytochrome c oxidase assembly by stabilizing newly synthesized Cox1.
|
|
| 2. |
- Bauerschmitt, Heike, et al.
(författare)
-
Ribosome-binding proteins Mdm38 and Mba1 display overlapping functions for regulation of mitochondrial translation
- 2010
-
Ingår i: Molecular Biology of the Cell. - 1059-1524 .- 1939-4586. ; 21:12, s. 1937-1944
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Biogenesis of respiratory chain complexes depends on the expression of mitochondrial-encoded subunits. Their synthesis occurs on membrane-associated ribosomes and is probably coupled to their membrane insertion. Defects in expression of mitochondrial translation products are among the major causes of mitochondrial disorders. Mdm38 is related to Letm1, a protein affected in Wolf-Hirschhorn syndrome patients. Like Mba1 and Oxa1, Mdm38 is an inner membrane protein that interacts with ribosomes and is involved in respiratory chain biogenesis. We find that simultaneous loss of Mba1 and Mdm38 causes severe synthetic defects in the biogenesis of cytochrome reductase and cytochrome oxidase. These defects are not due to a compromised membrane binding of ribosomes but the consequence of a mis-regulation in the synthesis of Cox1 and cytochrome b. Cox1 expression is restored by replacing Cox1-specific regulatory regions in the mRNA. We conclude, that Mdm38 and Mba1 exhibit overlapping regulatory functions in translation of selected mitochondrial mRNAs.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Richter, Katharina N., et al.
(författare)
-
Glyoxal as an alternative fixative to formaldehyde in immunostaining and super-resolution microscopy
- 2018
-
Ingår i: EMBO Journal. - : WILEY. - 0261-4189 .- 1460-2075. ; 37:1, s. 139-159
-
Tidskriftsartikel (refereegranskat)abstract
- Paraformaldehyde (PFA) is the most commonly used fixative for immunostaining of cells, but has been associated with various problems, ranging from loss of antigenicity to changes in morphology during fixation. We show here that the small dialdehyde glyoxal can successfully replace PFA. Despite being less toxic than PFA, and, as most aldehydes, likely usable as a fixative, glyoxal has not yet been systematically tried in modern fluorescence microscopy. Here, we tested and optimized glyoxal fixation and surprisingly found it to be more efficient than PFA-based protocols. Glyoxal acted faster than PFA, cross-linked proteins more effectively, and improved the preservation of cellular morphology. We validated glyoxal fixation in multiple laboratories against different PFA-based protocols and confirmed that it enabled better immunostainings for a majority of the targets. Our data therefore support that glyoxal can be a valuable alternative to PFA for immunostaining.
|
|
| 6. |
- van der Laan, Martin, et al.
(författare)
-
Motor-free mitochondrial presequence translocase drives membrane integration of preproteins
- 2007
-
Ingår i: Nature Cell Biology. - : Springer Science and Business Media LLC. - 1465-7392 .- 1476-4679. ; 9:10, s. 1152-1159
-
Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial inner membrane is the central energy-converting membrane of eukaryotic cells. the electrochemical proton gradient generated by the respiratory chain drives the ATP synthase. to maintain this proton-motive force, the inner membrane forms a tight barrier and strictly controls the translocation of ions(1). However, the major preprotein transport machinery of the inner membrane, termed the presequence translocase, translocates polypeptide chains into or across the membrane(2-9). Different views exist of the molecular mechanism of the translocase, in particular of the coupling with the import motor of the matrix(8,10,11). Wehave reconstituted preprotein transport into the mitochondrial inner membrane by incorporating the purified presequence translocase into cardiolipin-containing liposomes. We show that the motor-free form of the presequence translocase integrates preproteins into the membrane. the reconstituted presequence translocase responds to targeting peptides and mediates voltage-driven preprotein translocation, lateral release and insertion into the lipid phase. thus, the minimal system for preprotein integration into the mitochondrial inner membrane is the presequence translocase, a cardiolipin-rich membrane and a membrane potential.
|
|
| 7. |
- Österberg, Marie, 1972-
(författare)
-
What’s in? What’s out? And how did it get there? : Studies on topologies and insertion of membrane proteins
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Because of their hydrophobic and hydrophilic nature and the need for a lipid bilayer for retaining the native structure, membrane proteins are hard to study. Nevertheless, they are important, as many of our diseases are related to membrane proteins and around 60% of the different pharmaceutical drugs are directed against a membrane proteins [1]. There are many ways to study a protein, you can study function, structure, how the protein is targeted and inserted into its specific organelle, the interactions with other proteins or ligands etc. In the absence of a high-resolution structure, a topology model for a membrane protein is often useful. We have obtained reliable topologies for 546 of the membrane proteins going through the secretory pathways in S. cerevisiae by combining experimental data with topology prediction programs. In addition we have produced topology models for over 15,000 membrane proteins from 38 sequenced eukaryotic genomes using homology to the experimentally determined group. We also examined the growth rates and tolerance to certain stress conditions for our large set of clones that over-express membrane proteins. This provides important information both for structural studies of membrane proteins where large amounts of protein is needed for further studies, and for getting some insight in the function of specific proteins. Finally we have studied the integration of membrane proteins by the Tim23 translocon in the inner membrane of mitochondria. We have investigated the hydrophobicity required for efficient integration of transmembrane (TM) helices by Tim23. From this data we have derived an in vivo hydrophobicity scale for the insertion of different amino acids into the inner membrane of the mitochondria, and have made a comparison with a previously determined hydrophobicity scale for the ER translocon Sec61. We concluded that charged residues flanking the TM segment are of major importance for insertion into the membrane. We therefore further investigated the importance of charged residues flanking the first, weakly hydrophobic, TM segment in the mitochondrial inner membrane protein Mgm1p with regard to membrane insertion by the Tim23 complex.
|
|
