scholarly journals Pet191 Is a Cytochrome c Oxidase Assembly Factor in Saccharomyces cerevisiae

2008 ◽  
Vol 7 (8) ◽  
pp. 1427-1431 ◽  
Author(s):  
Oleh Khalimonchuk ◽  
Kevin Rigby ◽  
Megan Bestwick ◽  
Fabien Pierrel ◽  
Paul A. Cobine ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Disulfide Linkages ◽  
Assembly Factor ◽  
Oligomeric Complex

ABSTRACT The twin-Cx9C motif protein Pet191 is essential for cytochrome c oxidase maturation. The motif Cys residues are functionally important and appear to be present in disulfide linkages within a large oligomeric complex associated with the mitochondrial inner membrane. The import of Pet191 differs from that of other twin-Cx9C motif class of proteins in being independent of the Mia40 pathway.

scholarly journals The m-AAA Protease Processes Cytochrome c Peroxidase Preferentially at the Inner Boundary Membrane of Mitochondria

2009 ◽  
Vol 20 (2) ◽  
pp. 572-580 ◽  
Author(s):  
Ida E. Suppanz ◽  
Christian A. Wurm ◽  
Dirk Wenzel ◽  
Stefan Jakobs
Keyword(s):  
Cytochrome C ◽  
Protein Quality ◽  
Cytochrome C Peroxidase ◽  
Inner Membrane ◽  
Proteolytic Activation ◽  
Mitochondrial Inner Membrane ◽  
Functional Differences ◽  
Oligomeric Complex ◽  
Quantitative Immunoelectron Microscopy ◽  
Boundary Membrane

The m-AAA protease is a conserved hetero-oligomeric complex in the inner membrane of mitochondria. Recent evidence suggests a compartmentalization of the contiguous mitochondrial inner membrane into an inner boundary membrane (IBM) and a cristae membrane (CM). However, little is known about the functional differences of these subdomains. We have analyzed the localizations of the m-AAA protease and its substrate cytochrome c peroxidase (Ccp1) within yeast mitochondria using live cell fluorescence microscopy and quantitative immunoelectron microscopy. We find that the m-AAA protease is preferentially localized in the IBM. Likewise, the membrane-anchored precursor form of Ccp1 accumulates in the IBM of mitochondria lacking a functional m-AAA protease. Only upon proteolytic cleavage the mature form mCcp1 moves into the cristae space. These findings suggest that protein quality control and proteolytic activation exerted by the m-AAA protease take place preferentially in the IBM pointing to significant functional differences between the IBM and the CM.

scholarly journals Intramitochondrial sorting of the precursor to yeast cytochrome c oxidase subunit Va.

1993 ◽  
Vol 121 (5) ◽  
pp. 1021-1029 ◽  
Author(s):  
B R Miller ◽  
M G Cumsky
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Mitochondrial Protein ◽  
Inner Membrane ◽  
Oxidase Subunit ◽  
Mitochondrial Inner Membrane ◽  
The Matrix ◽  
Inner Membrane Protein ◽  
Membrane Spanning ◽  
Mitochondrial Heat Shock Protein

We have continued our studies on the import pathway of the precursor to yeast cytochrome c oxidase subunit Va (pVa), a mitochondrial inner membrane protein. Previous work on this precursor demonstrated that import of pVa is unusually efficient, and that inner membrane localization is directed by a membrane-spanning domain in the COOH-terminal third of the protein. Here we report the results of studies aimed at analyzing the intramitochondrial sorting of pVa, as well as the role played by ancillary factors in import and localization of the precursor. We found that pVa was efficiently imported and correctly sorted in mitochondria prepared from yeast strains defective in the function of either mitochondrial heat shock protein (hsp)60 or hsp70. Under identical conditions the import and sorting of another mitochondrial protein, the precursor to the beta subunit of the F1 ATPase, was completely defective. Consistent with previous results demonstrating that the subunit Va precursor is loosely folded, we found that pVa could be efficiently imported into mitochondria after translation in wheat germ extracts. This results suggests that normal levels of extramitochondrial hsp70 are also not required for import of the protein. The results of this study enhance our understanding of the mechanism by which pVa is routed to the mitochondrial inner membrane. They suggest that while the NH2 terminus of pVa is exposed to the matrix and processed by the matrix metalloprotease, the protein remains anchored to the inner membrane before being assembled into a functional holoenzyme complex.

scholarly journals The Yeast Aac2 Protein Exists in Physical Association with the Cytochromebc1-COX Supercomplex and the TIM23 Machinery

2008 ◽  
Vol 19 (9) ◽  
pp. 3934-3943 ◽  
Author(s):  
Mary K. Dienhart ◽  
Rosemary A. Stuart
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Affinity Purification ◽  
Yeast Saccharomyces Cerevisiae ◽  
Present Evidence ◽  
Cytochrome Bc ◽  
Saccharomyces Cerevisiae Mitochondria ◽  
Mitochondrial Inner Membrane ◽  
Physical Association

The ADP/ATP carrier (AAC) proteins play a central role in cellular metabolism as they facilitate the exchange of ADP and ATP across the mitochondrial inner membrane. We present evidence here that in yeast (Saccharomyces cerevisiae) mitochondria the abundant Aac2 isoform exists in physical association with the cytochrome c reductase (cytochrome bc1)-cytochrome c oxidase (COX) supercomplex and its associated TIM23 machinery. Using a His-tagged Aac2 derivative and affinity purification studies, we also demonstrate here that the Aac2 isoform can be affinity-purified with other AAC proteins. Copurification of the Aac2 protein with the TIM23 machinery can occur independently of its association with the fully assembled cytochrome bc1-COX supercomplex. In the absence of the Aac2 protein, the assembly of the cytochrome bc1-COX supercomplex is perturbed, whereby a decrease in the III2-IV2assembly state relative to the III2-IV form is observed. We propose that the association of the Aac2 protein with the cytochrome bc1-COX supercomplex is important for the function of the OXPHOS complexes and for the assembly of the COX complex. The physiological implications of the association of AAC with the cytochrome bc1-COX-TIM23 supercomplex are also discussed.

scholarly journals Interactions amongCOX1,COX2, andCOX3mRNA-specific Translational Activator Proteins on the Inner Surface of the Mitochondrial Inner Membrane ofSaccharomyces cerevisiae

2003 ◽  
Vol 14 (1) ◽  
pp. 324-333 ◽  
Author(s):  
Sushma Naithani ◽  
Scott A. Saracco ◽  
Christine A. Butler ◽  
Thomas D. Fox
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Translation System ◽  
Mitochondrial Translation ◽  
Inner Membrane ◽  
Activator Proteins ◽  
The Core ◽  
Mitochondrial Inner Membrane ◽  
The Matrix ◽  
Translational Activator

The core of the cytochrome c oxidase complex is composed of its three largest subunits, Cox1p, Cox2p, and Cox3p, which are encoded in mitochondrial DNA of Saccharomyces cerevisiae and inserted into the inner membrane from the inside. Mitochondrial translation of the COX1,COX2, and COX3 mRNAs is activated mRNA specifically by the nuclearly coded proteins Pet309p, Pet111p, and the concerted action of Pet54p, Pet122p, and Pet494p, respectively. Because the translational activators recognize sites in the 5′-untranslated leaders of these mRNAs and because untranslated mRNA sequences contain information for targeting their protein products, the activators are likely to play a role in localizing translation. Herein, we report physical associations among the mRNA-specific translational activator proteins, located on the matrix side of the inner membrane. These interactions, detected by coimmune precipitation and by two-hybrid experiments, suggest that the translational activator proteins could be organized on the surface of the inner membrane such that synthesis of Cox1p, Cox2p, and Cox3p would be colocalized in a way that facilitates assembly of the core of the cytochrome c oxidase complex. In addition, we found interactions between Nam1p/Mtf2p and the translational activators, suggesting an organized delivery of mitochondrial mRNAs to the translation system.

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