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.

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 Mba1, a Novel Component of the Mitochondrial Protein Export Machinery of the Yeast Saccharomyces cerevisiae

2001 ◽  
Vol 153 (5) ◽  
pp. 1085-1096 ◽  
Author(s):  
Marc Preuss ◽  
Klaus Leonhard ◽  
Kai Hell ◽  
Rosemary A. Stuart ◽  
Walter Neupert ◽  
...  
Keyword(s):  
Mitochondrial Protein ◽  
Protein Export ◽  
Mitochondrial Translation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Inner Membrane ◽  
Protein Insertion ◽  
Mitochondrial Inner Membrane ◽  
The Matrix ◽  
Biogenesis Of Mitochondria ◽  
Inner Membrane Protein

The biogenesis of mitochondria requires the integration of many proteins into the inner membrane from the matrix side. The inner membrane protein Oxa1 plays an important role in this process. We identified Mba1 as a second mitochondrial component that is required for efficient protein insertion. Like Oxa1, Mba1 specifically interacts both with mitochondrial translation products and with conservatively sorted, nuclear-encoded proteins during their integration into the inner membrane. Oxa1 and Mba1 overlap in function and substrate specificity, but both can act independently of each other. We conclude that Mba1 is part of the mitochondrial protein export machinery and represents the first component of a novel Oxa1-independent insertion pathway into the mitochondrial inner membrane.

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 Characterization of Mmp37p, aSaccharomyces cerevisiaeMitochondrial Matrix Protein with a Role in Mitochondrial Protein Import

2006 ◽  
Vol 17 (9) ◽  
pp. 4051-4062 ◽  
Author(s):  
Michelle R. Gallas ◽  
Mary K. Dienhart ◽  
Rosemary A. Stuart ◽  
Roy M. Long
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Temperature Sensitive ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Close Proximity ◽  
The Matrix ◽  
Targeting Signal

Many mitochondrial proteins are encoded by nuclear genes and after translation in the cytoplasm are imported via translocases in the outer and inner membranes, the TOM and TIM complexes, respectively. Here, we report the characterization of the mitochondrial protein, Mmp37p (YGR046w) and demonstrate its involvement in the process of protein import into mitochondria. Haploid cells deleted of MMP37 are viable but display a temperature-sensitive growth phenotype and are inviable in the absence of mitochondrial DNA. Mmp37p is located in the mitochondrial matrix where it is peripherally associated with the inner membrane. We show that Mmp37p has a role in the translocation of proteins across the mitochondrial inner membrane via the TIM23-PAM complex and further demonstrate that substrates containing a tightly folded domain in close proximity to their mitochondrial targeting sequences display a particular dependency on Mmp37p for mitochondrial import. Prior unfolding of the preprotein, or extension of the region between the targeting signal and the tightly folded domain, relieves their dependency for Mmp37p. Furthermore, evidence is presented to show that Mmp37 may affect the assembly state of the TIM23 complex. On the basis of these findings, we hypothesize that the presence of Mmp37p enhances the early stages of the TIM23 matrix import pathway to ensure engagement of incoming preproteins with the mtHsp70p/PAM complex, a step that is necessary to drive the unfolding and complete translocation of the preprotein into the matrix.

A genetic link between an mRNA-specific translational activator and the translation system in yeast mitochondria.

Genetics ◽  
1990 ◽  
Vol 125 (3) ◽  
pp. 495-503 ◽  
Author(s):  
P Haffter ◽  
T W McMullin ◽  
T D Fox
Keyword(s):  
Mitochondrial Gene ◽  
Mitochondrial Protein ◽  
Open Reading Frame ◽  
Null Alleles ◽  
Translation System ◽  
Amino Acid Residues ◽  
Mitochondrial Translation ◽  
Reading Frame ◽  
Large Deletions ◽  
Translational Activator

Abstract Translation of the Saccharomyces cerevisiae mitochondrial mRNA encoding cytochrome c oxidase subunit III (coxIII) specifically requires the products of at least three nuclear genes, PET122, PET494 and PET54. pet122 mutations that remove 24-67 amino acid residues from the carboxyterminus of the gene product were found to be suppressed by unlinked nuclear mutations. These unlinked suppressors fail to suppress both a pet122 missense mutation and a complete pet122 deletion. One of the suppressor mutations causes a heat-sensitive nonrespiratory growth phenotype in an otherwise wild-type strain and reduces translation of all mitochondrial gene products in cells grown at high temperature. This suppressor maps to a newly identified gene on chromosome XV termed PET123. The sequence of a DNA fragment carrying PET123 contains one major open reading frame encoding a basic protein of 318 amino acids. Inactivation of the chromosomal copy of PET123 by interruption of this open reading frame causes cells to become rho- (sustain large deletions in their mtDNA). This phenotype is characteristic for null alleles of genes whose products are essential for general mitochondrial protein synthesis. Thus our data strongly suggest that the PET123 protein is a component of the mitochondrial translation apparatus that interacts directly with the coxIII-mRNA-specific translational activator PET122.

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