Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Subunit VIII of mammalian cytochrome c oxidase (COX; EC 1.9.3.1) exists in at least two isoforms, because different but related polypeptides have been identified in COX isolated from liver and heart of both beef and pig. We have isolated a full length cDNA specifying subunit VIII of human COX from a human liver cDNA library. Sequences hybridizing to this cDNA are present at only one site, the COX8 locus, on human chromosome 11q12-q13. The deduced human polypeptide is 58% identical with COX VIII isolated from beef liver, but only 38% identical with COX VIII isolated from beef heart. Transcriptional analysis shows that an mRNA identical with the isolated cDNA is present in abundant amounts not only in human and monkey liver tissue, but in heart and skeletal muscle as well, tissues not known previously to contain this isoform. Since the only COX VIII subunit found in human heart agrees 100% with the polypeptide deduced from this coxVIII cDNA, it may well be that, in distinction to other mammals, only one form of COX VIII exists in primates.
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PMID:A gene specifying subunit VIII of human cytochrome c oxidase is localized to chromosome 11 and is expressed in both muscle and non-muscle tissues. 254 73

The yeast nuclear SCO1 gene is required for accumulation of the mitochondrially synthesized cytochrome c oxidase subunits I and II (COXI and COXII). We cloned and characterized the SCO1 gene. It codes for a 0.9 kb transcript. DNA sequence analysis predicts a 33 kDa protein. As shown by in vitro transcription and translation experiments in combination with import studies on isolated mitochondria, this protein is matured into a 30 kDa polypeptide which is tightly associated with a mitochondrial membrane. The possible function of the SCO1 gene product in the assembly of cytochrome c oxidase is discussed.
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PMID:Accumulation of the cytochrome c oxidase subunits I and II in yeast requires a mitochondrial membrane-associated protein, encoded by the nuclear SCO1 gene. 254 7

Cytochrome c oxidase was purified from mitochondria of Euglena gracilis and separated into 15 different polypeptide subunits by polyacrylamide gel electrophoresis. All 15 subunits copurify through various purification procedures, and the subunit composition of the isolated enzyme is identical to that of the immunoprecipitated one. Therefore, the 15 protein subunits represent integral components of the Euglena oxidase. In an in vitro protein-synthesizing system using isolated mitochondria, polypeptides 1-3 were radioactive labeled in the presence of [35S]methionine. This further identifies these polypeptides with the three largest subunits of cytochrome c oxidase encoded by mitochondrial DNA in other eukaryotic organisms. By subtraction, the other 12 subunits can be assigned to nuclear genes. The isolated Euglena oxidase was highly active with Euglena cytochrome c558 and has monophasic kinetics. Using horse cytochrome c550 as a substrate, activity of the isolated oxidase was rather low. These findings correlate with the oxidase activity of mitochondrial membranes. Again, reactivity was low with cytochrome c550 and 35-fold higher with the Euglena cytochrome c558. The data show that the cytochrome c oxidase of the protist Euglena is different from other eukaryotic cytochrome c oxidases in number and size of subunits, and also with regard to kinetic properties and substrate specificity.
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PMID:Cytochrome c oxidase of Euglena gracilis: purification, characterization, and identification of mitochondrially synthesized subunits. 254 70

The COX5a and COX5b genes encode divergent forms of yeast cytochrome c oxidase subunit V. Although the polypeptide products of the two genes are functionally interchangeable, it is the Va subunit that is normally found in preparations of yeast mitochondria and cytochrome c oxidase. We show here that the predominance of subunit Va stems in part from the differential response of the two genes to the presence of molecular oxygen. Our results indicate that during aerobic growth, COX5a levels were high, while COX5b levels were low. Anaerobically, the pattern was reversed; COX5a levels dropped sevenfold, while those of COX5b were elevated sevenfold. Oxygen appeared to act at the level of transcription through heme, since the addition of heme restored an aerobic pattern of transcription to anaerobically grown cells and the effect of anaerobiosis on COX5 transcription was reproduced in strains containing a mutation in the heme-biosynthetic pathway (hem1). In conjunction with the oxygen-heme response, we determined that the product of the ROX1 gene, a trans-acting regulator of several yeast genes controlled by oxygen, is also involved in COX5 expression. These results, as well as our observation that COX5b expression varied significantly in certain yeast strains, indicate that the COX5 genes undergo a complex pattern of regulation. This regulation, especially the increase in COX5b levels anaerobically, may reflect an attempt to modulate the activity of a key respiratory enzyme in response to varying environmental conditions. The results presented here, as well as those from other laboratories, suggest that the induction or derepression of certain metabolic enzymes during anaerobiosis may be a common and important physiological response in yeast cells.
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PMID:Inverse regulation of the yeast COX5 genes by oxygen and heme. 254 55

A polypeptide chain-terminating mutation (M5631) previously has been shown to be a +1T insertion in the yeast mitochondrial gene oxi1, coding for subunit II of the cytochrome c oxidase. A spontaneously arisen frameshift suppressor (mfs-1) that is mitochondrially inherited suppresses this mutation to a considerable extent. The suppressor mutation was mapped by genetic and molecular analyses in the mitochondrial tRNASer-var1 region of the mitochondrial genome of the yeast S. cerevisiae. Genetic analyses show that the suppressor mfs-1 does not suppress other known mitochondrial frameshift mutations, or missense and nonsense mutations.
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PMID:A mitochondrial frameshift suppressor maps in the tRNASer-var1 region of the mitochondrial genome of the yeast S. cerevisiae. 254 83

Subunit II of cytochrome c oxidase is a mitochondrially encoded protein required for cellular respiration. A respiration-deficient yeast strain has been isolated and shown genetically to carry a mutation in the subunit II structural gene COX2. The respiration-deficient strain produces no subunit II polypeptide and is missing two major transcripts of the subunit II gene. The mutation, first mapped by rho- recombinational rescue to the 5' end of the gene, has been localized precisely, by DNA sequencing, 58 nucleotides upstream of the COX2 ATG initiation codon. The mutant strain carries a single nucleotide change (A to T) relative to the wild type sequence. This mutation occurs in a sequence with substantial homology to a previously identified yeast mitochondrial promoter consensus sequence. These results provide the first in vivo evidence for the importance of the consensus sequence for promoter function.
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PMID:Isolation and characterization of a yeast strain carrying a mutation in the mitochondrial promoter for COX2. 254 60

The mammalian cytochrome c oxidase is a complex of 13 different subunits. We present the full amino acid sequence of the one remaining uncharacterized subunit, subunit IHQ in the nomenclature used here, VIIb in the numbering system of Kadenbach and colleagues (e.g. Kadenbach, B., and Merle, P. (1981) FEBS Lett. 135, 1-11). A partial protein sequence was obtained from the purified subunit isolated by gel filtration procedures. This information was used to synthesize an oligonucleotide probe which was then used to isolate a cDNA clone encoding the subunit. This cDNA for subunit IHQ is 480 base pairs long and encodes a polypeptide which is either 83 or 88 amino acids long, including an N-terminal leader sequence of either 27 or 32 residues. The molecular weight of the mature subunit IHQ is 6350 based on the amino acid sequence deduced from the gene. The leader sequence is typical of other mitochondrial target sequences in having several positively charged residues but no negatively charged side chains.
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PMID:Cloning and sequencing of the cDNA for a 13th different subunit (IHQ) of beef heart cytochrome c oxidase. 255 Apr 62

A 70 kD protein, which we have named mitoskelin, is highly enriched in cytoskeletal preparations from bovine cardiac muscle. Mitoskelin has three main variants with isoelectric points between 5.6 and 5.8. Immunoblotting with polyclonal antibodies directed against mitoskelin shows that, like intermediate filament proteins, the majority of mitoskelin resists solubilization from a myocardial homogenate by a series of extraction solutions ranging from very low salt to 0.6 M KI buffers and by 0.1-1% Nonidet P-40 detergent. By double-label immunofluorescence on cells and tissues, mitoskelin is colocalized with the mitochondrial marker cytochrome c oxidase. Mitoskelin is associated with the inner membranes of mitochondria as shown by immunoelectron microscopy and immunoblotting. Immunological cross-reactivity and similarities of molecular weight, pI, distribution, and chromatographic properties indicate that mitoskelin is the 70 kD component of complex I (NADH: ubiquinone oxidoreductase), a portion of the mitochondrial oxidative phosphorylation system. No function or activity has yet been demonstrated for the 70 kD component of the 25-polypeptide complex I. Dialysis against physiological buffers allows purified, urea-solubilized mitoskelin to form 10 nm wide filamentous structures that do not closely resemble intermediate filaments. These results suggest the exciting possibility that mitochondria may contain a membrane-associated filamentous skeleton.
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PMID:Mitoskelin: a mitochondrial protein found in cytoskeletal preparations. 267 50

In Saccharomyces cerevisiae, subunit V of the inner mitochondrial membrane protein complex cytochrome c oxidase is encoded by two nonidentical genes, COX5a and COX5b. Both genes are present as single copies in S. cerevisiae and in several other Saccharomyces species. Nucleotide sequencing studies with the S. cerevisiae COX5 genes reveal that they encode proteins of 153 and 151 amino acids, respectively. Overall, the coding sequences of COX5a and COX5b have nucleotide and protein homologies of 67 and 66%, respectively. They are saturated for nucleotide substitutions that result in a synonomous codon, indicating a long divergence time between these two genes. Nucleotide sequences flanking the COX5a and COX5b coding regions exhibit no significant homology. The COX5a protein, pre-subunit Va, contains a 20-amino-acid leader peptide, whereas the COX5b protein, pre-subunit Vb, contains a 17-amino-acid leader peptide. These two leader peptides exhibit only 45% homology in the primary sequence, but have similar predicted secondary structures. By analyzing the RNA transcripts from both genes we have found that COX5a is a contiguous gene but that COX5b contains an intron. Surprisingly, the COX5b intron interrupts the AUG codon that initiates translation of the pre-subunit Vb polypeptide and contains a 5' donor splice sequence that differs from that normally found in yeast introns.
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PMID:Structural analysis of two genes encoding divergent forms of yeast cytochrome c oxidase subunit V. 282 89

Bovine heart cytochrome c oxidase, depleted of polypeptide subunits by alkaline detergent treatment, was characterized with respect to metal content, optical spectral properties, and oxidase activity. Treatment with 1.0% Triton X-100 at pH 9.5 followed by anion-exchange chromatography caused removal of subunit III, subunit VII, and polypeptides a and b. The metal atom stoichiometries of the control and the polypeptide-depleted enzyme were in both cases 2.5Cu/2Fe/1Zn/1Mg with metal-to-protein ratios significantly greater in the latter. The treated enzyme exhibited a red shifted oxidized Soret maximum and bound carbon monoxide upon reduction. Activity was markedly decreased by the treatment but was restored to control levels by incubation with 0.3% Tween 80 at pH 6.0. Therefore, subunit III, subunit VII, polypeptide a, and polypeptide b do not contain Cu, Fe, Zn, or Mg and are not essential for reduction of O2 by ferrocytochrome c.
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PMID:Metals and activity of bovine heart cytochrome c oxidase are independent of polypeptide subunits III, VII, a, and b. 282 90


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