Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mitochondria contain hundreds of proteins, most of which are encoded by the nucleus. In neurons, distal dendrites and axon terminals can be separated from the nucleus by a great distance, and the mechanism by which precursor proteins reach distal neuronal processes is not well understood. While our previous study on cytochrome oxidase suggests a post-translational mechanism of delivery, it is not known whether precursor proteins reach their target processes before or after incorporation into mitochondria. In order to localize only precursor proteins and not the mature form of the subunit in neurons, we generated polyclonal antibodies against synthetic presequence polypeptides specific to nuclear-encoded subunit IV precursor protein of rat brain cytochrome oxidase. We found that the precursors were located not only in neuronal cell bodies, but also in dendrites and axon terminals. This indicates that the conversion of these precursors to their mature form is not confined to the cell body but occurs in dendrites and axons as well. At the electron microscopic level, an overwhelming majority of immunoreaction product was found within mitochondria, suggesting that precursor proteins are transported to neuronal processes mainly within mitochondria, and that their half-lives are much longer in neurons than in yeast and rat hepatocytes. The precursor pool was downregulated in the rat superior colliculus after monocular enucleation, indicating that precursor synthesis and/or degradation is regulated by neuronal functional activity. These results also suggest that local functional demands may play an important role in controlling the processing of precursors and the assembly of holoenzymes in dendrites and axon terminals. This allows neurons to regulate enzyme levels locally, precisely, and rapidly.
 ...
PMID:Nuclear-encoded mitochondrial precursor protein: intramitochondrial delivery to dendrites and axon terminals of neurons and regulation by neuronal activity. 808 39

A new property of the presequence of the mitochondrial precursor protein cytochrome oxidase subunit IV is presented. This mitochondrial presequence induces interbilayer contacts between large unilamellar vesicles consisting of phosphatidylcholine and cardiolipin. The presequence-vesicle aggregates can be dissociated by applying a membrane potential across the bilayers (negative inside). These effects require the presence of cardiolipin and are not observed for other negatively charged phospholipids. We propose a role for the presequence in the formation and dissociation of mitochondrial contact sites.
 ...
PMID:A novel property of a mitochondrial presequence. Its ability to induce cardiolipin-specific interbilayer contacts which are dissociated by a transmembrane potential. 839 51

In vitro synthesized Pet1402 precursor protein is very rapidly and efficiently imported into isolated mitochondria. The import depends on a membrane potential and functional mtHsp70. The mitochondrial targeting sequence of the Pet1402 precursor protein is removed by the matrix processing peptidase MPP and the mature protein is firmly embedded in the inner mitochondrial membrane. The Pet1402 protein is required for the integrity of the cytochrome oxidase and ubiquinol-cytochrome c oxidoreductase complexes.
 ...
PMID:Mitochondrial inner membrane bound Pet1402 protein is rapidly imported into mitochondria and affects the integrity of the cytochrome oxidase and ubiquinol-cytochrome c oxidoreductase complexes. 942 97

Two genes encoding cytochrome c oxidase subunits, Cox2a and Cox2b, are present in the nuclear genomes of apicomplexan parasites and show sequence similarity to corresponding genes in chlorophycean algae. We explored the presence of COX2A and COX2B subunits in the cytochrome c oxidase of Toxoplasma gondii. Antibodies were raised against a synthetic peptide containing a 14-residue fragment of the COX2A polypeptide and against a hexa-histidine-tagged recombinant COX2B protein. Two distinct immunochemical stainings localized the COX2A and COX2B proteins in the parasite's mitochondria. A mitochondria-enriched fraction exhibited cyanide-sensitive oxygen uptake in the presence of succinate. T. gondii mitochondria were solubilized and subjected to Blue Native Electrophoresis followed by second dimension electrophoresis. Selected protein spots from the 2D gels were subjected to mass spectrometry analysis and polypeptides of mitochondrial complexes III, IV and V were identified. Subunits COX2A and COX2B were detected immunochemically and found to co-migrate with complex IV; therefore, they are subunits of the parasite's cytochrome c oxidase. The apparent molecular mass of the T. gondii mature COX2A subunit differs from that of the chlorophycean alga Polytomella sp. The data suggest that during its biogenesis, the mitochondrial targeting sequence of the apicomplexan COX2A precursor protein may be processed differently than the one from its algal counterpart.
 ...
PMID:The polypeptides COX2A and COX2B are essential components of the mitochondrial cytochrome c oxidase of Toxoplasma gondii. 1803 50


<< Previous 1 2