Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.9.3.1 (cytochrome oxidase)
8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

These studies describe the properties of three mit- mutants designated EM17, EM25, and PZ1, all mapping at two closely linked sites near one of the boundaries of the region of the mitochondrial genome concerned with the specification of cytochrome b. They all exhibit complex phenotypes affecting cytochrome b, cytochrome aa3, and additional polypeptides not found in the wild type. In the case of EM 17 this complexity can be ascribed to the presence of two mutations induced in the course of the initial mutagenic treatment: one, the cob2 mutation proper, is responsible for the loss of cytochrome b which is replaced by an altered, functionally inactive polypeptide, cytochrome b. This polypeptide can be further modified, or even eliminated, by the controlled introduction of another mutation in the cob1 segment of the cob region. The reduction in cytochrome oxidase subunit I, responsible for the effects on cytochrome aa3 and enzymatic activity in EM17, is due to a second (not mit-) mutation that has been located in the par1-proximal segment of the oxi3 region. This second mutation as well as the cob mutation can be overcome, and the respective aspect of wild type function restored to EM17, by recombination with rho- strains retaining the appropriate segment(s) of the wild type genome. The phenotype of the other two mutants is due to a single mutagenic event. This conclusion is confirmed by their ability to restore wild type functions by reversion. The mutation in EM25 appears to be due to a frameshift, which has led to premature chain termination, producing a polypeptide of Mr = 15,000 related to apocytochrome b. This change is accompanied by a decrease in the amount of subunit I of cytochrome oxidase. Revertants fall into three classes: on galactose two produce a polypeptide indistinguishable from apocytochrome b, but vary in its amount, while the third fails to increase apocytochrome b above mutant levels. Production of subunit I is increased but fails to reach wild type levels. Complete restoration of wild type functions can, however, be obtained by recombination of EM25 with rho- (cob2+) strains. Mutation PZ1 results in a complete absence of any polypeptide related to apocytochrome b and of cytochrome oxidase subunit I. These cells produce a novel polypeptide with a Mr = 45,000 not found in the wild type, and unrelated to all its normal polypeptides. Reversion or recombination with rho- (cob2+) strains results in virtually complete restoration of all wild type functions and the elimination of the novel polypeptide.
...
PMID:Regulatory interaction between mitochondrial genes. II. Detailed characterization of novel mutants mapping within one cluster in the cob2 region. 21 40

Eight respiratory-deficient mutants of Chlamydomonas reinhardtii have been isolated after mutagenic treatment with acriflavine or ethidium bromide. They are characterized by their inability to grow or their very reduced growth under heterotrophic conditions. One mutation (Class III) is of nuclear origin whereas the seven remaining mutants (Classes I and II) display a predominantly paternal mt- inheritance, typical of mutations residing in the mitochondrial DNA. Biochemical analysis has shown that all mutants are deficient in the cyanide-sensitive cytochrome pathway of the respiration whereas the alternative pathway is still functional. Measurements of complexes II + III (antimycin-sensitive succinate-cytochrome c oxido-reductase) and complex IV (cytochrome c oxidase) activities allowed to conclude that six mutations have to be localized in the mitochondrial apocytochrome b (COB) gene, one in the mitochondrial cytochrome oxidase subunit I (COI) gene and one in a nuclear gene encoding a component of the cytochrome oxidase complex. By using specific probes, we have moreover demonstrated that five mutants (Class II mutants) contain mitochondrial DNA molecules deleted in the terminal end containing the COB gene and the telomeric region; they also possess dimeric molecules resulting from end-to-end junctions of deleted monomers. The two other mitochondrial mutants (Class I) have no detectable gross alteration. Class I and Class II mutants can also be distinguished by the pattern of transmission of the mutation in crosses. An in vivo staining test has been developed to identify rapidly the mutants impaired in cyanide-sensitive respiration.
...
PMID:Biochemical, genetic and molecular characterization of new respiratory-deficient mutants in Chlamydomonas reinhardtii. 155 49

The terminal cytochrome c1aa3 of the respiratory chain of Thermus thermophilus has been isolated and purified to homogeneity by a novel procedure. The two subunit proteins (55 and 33 kDa) have been characterized chemically. Computer searches with partial amino acid sequences obtained from both subunits show that the larger subunit belongs to the cytochrome oxidase subunit I protein family while the smaller covalently heme-binding subunit is not a cytochrome c1 but appears to be a fused protein between cytochrome c and cytochrome oxidase subunit II. With respect to the 16-S rRNA-derived phylogeny of procaryotes, the results show that the genetic information for an O2-reacting cytochrome oxidase (EC 1.9.3.1) existed already in early eubacteria.
...
PMID:Evidence for cytochrome oxidase subunit I and a cytochrome c--subunit II fused protein in the cytochrome 'c1aa3' of Thermus thermophilus. How old is cytochrome oxidase? 254 Sep 68

The gene coding for cytochrome oxidase subunit I (COI) was isolated from a genomic DNA library of the thermophilic bacterium PS3 and sequenced. The N-terminal of the COI protein was also sequenced to verify the initiation site of the reading frame. The deduced amino acid sequence of COI protein is composed of 536 amino acid residues and its molecular mass is 59,510. The protein is clearly homologous to the corresponding subunit in the mitochondrial cytochrome oxidase and similarly appears to have 12 trans-membrane segments. The proposed ligands to two hemes (cytochrome aa3) and a copper atom (CuB) in this protein (Holm et al. (1987) EMBO J. 6, 2819-2823) are conserved in the sequence.
...
PMID:Nucleotide sequence of the gene coding for cytochrome oxidase subunit I from the thermophilic bacterium PS3. 284 37

Transcripts for six Leishmania tarentolae maxicircle structural genes (cytochrome oxidase subunits I, II and III, cytochrome b, human mitochondrial unidentified reading frames 4 and 5) and several unidentified open reading frames were mapped, and the locations of the 5' ends determined by primer runoff analysis. All genes studied here are transcribed from the same strand as the 12S and 9S ribosomal RNAs except for the cytochrome oxidase subunit I gene. In two cases (ORF3 and ORF4, ORF5 and ORF6), a single transcript covers two contiguous overlapping reading frames. The 5' ends of the RNAs are located 20-64 nt from the putative translation initiation codons. Primary transcripts from a mitochondrial RNA preparation were 5' end-labeled with guanylyltransferase and alpha -32P-GTP; the major labeled species comigrated with the 12S and 9S mitochondrial rRNAs, and in addition there were at least four higher molecular weight labeled species.
...
PMID:Mapping and 5' end determination of kinetoplast maxicircle gene transcripts from Leishmania tarentolae. 299 21

The DNA sequence of approximately 80% of the transcribed region of the kinetoplast maxicircle DNA of Leishmania tarentolae was obtained, and structural genes were localized by comparison of the translated amino acid sequences with those of known mitochondrial genes from other organisms. By this method, the genes for cytochrome oxidase subunits I, II, and III, cytochrome b, and human mitochondrial unidentified reading frames 4 and 5 were identified. By comparing the amino acid sequences of the putative L. tarentolae genes with those of known genes, we conclude that TGA codes for tryptophan, as in most other mitochondrial systems. This is the only apparent change from the universal genetic code. The six identified structural genes show various degrees of divergence from the homologous genes in other species, with cytochrome oxidase subunit I being the most conserved and cytochrome oxidase subunit III being the least conserved. A comparison of the cytochrome b genes from L. tarentolae and Trypanosoma brucei showed that the ratio of transversions to transitions is 1:1, suggesting that these species diverged from each other more than 80 X 10(6) years ago. Several as yet unidentified open reading frames were also present in the maxicircle sequence. These data confirm that maxicircle DNA has a coding potential which typifies other mitochondrial systems.
...
PMID:Sequences of six genes and several open reading frames in the kinetoplast maxicircle DNA of Leishmania tarentolae. 609 60

We have analyzed the mitochondrial RNA of a yeast nuclear pet mutant with no cytochrome oxidase activity. The product of the gene affected in this mutant appears to be necessary for the correct maturation of the mitochondrial pre-mRNA of the cytochrome oxidase subunit I. It does not affect, however, the overall splicing of cytochrome b pre-mRNA or the intron excision of the 21S ribosomal RNA precursor. This gene has been isolated by genetic complementation in yeast, and its DNA sequence has been determined. It is transcribed, as detected by S1 mapping experiments, and could encode a protein of 436 amino acids.
...
PMID:Analysis of a yeast nuclear gene involved in the maturation of mitochondrial pre-messenger RNA of the cytochrome oxidase subunit I. 629 89

Differential screening of an adrenal cortex cDNA library for corticotropin (ACTH)-inducible genes led to the isolation of a group of cDNAs representing mitochondrial genes that encode subunits of cytochrome oxidase, ATPase, and NADH dehydrogenase. Northern blot analysis of RNA from cells stimulated by ACTH confirmed the induction of these genes by ACTH yet revealed major differences in the relative responses of the respective mRNAs. The levels of mRNAs for cytochrome oxidase subunit I and ATPase increased 2- to 4-fold and for NADH dehydrogenase subunit 3 increased 20-fold, whereas the levels of the mitochondrial 16S rRNA showed no change within 6 h of ACTH stimulation. These effects of ACTH on mitochondrial mRNA levels probably result from both activation of the H2 transcription unit that encodes mitochondrial mRNAs and alteration of mRNA stability. ACTH also increased the activity of cytochrome oxidase after 12 h of stimulation. Examination of the tissue specificity of expression of five mitochondrial genes showed a wide range of RNA levels among 11 tissues but high correlations between individual RNA levels, consistent with a coordinated expression of the mitochondrial genes, although at different levels in each cell type. Proportionately high levels of mitochondrial mRNAs were found in adrenal cortex, probably reflecting a stimulatory effect of ACTH in vivo. Overall, the results indicate that ACTH enhances the energy-producing capacity of adrenocortical cells.
...
PMID:Mitochondrial-genome-encoded RNAs: differential regulation by corticotropin in bovine adrenocortical cells. 750 67

A new search for mitochondrial respiratory deficient mutants (Mit-) has been undertaken in order to accumulate a large number of point mutations in the coding portions of cytochrome-c-oxidase catalytic subunits and cytochrome b. Therefore, a mitochondrial DNA which retains the exons and lacks all the introns of the cytochrome oxidase subunit I and of the cytochrome-b split genes has been introduced into a strain carrying a nuclear recessive mutation affecting the adenine-nucleotide translocator, the op1 mutation, which is known to prevent the accumulation of large deletion petite mutants and this was used as the parental strain. After a moderate MnCl2 mutagenesis in order to limit multiple mutations, 105 Mit- mutants were isolated from 15,000 mutagenised clones in Saccharomyces cerevisiae. Mutations were mapped to the three catalytic subunits encoding genes (COX1, COX2 and COX3) of the cytochrome-c oxidase (70 mutations) and to the cytochrome-b gene (15 mutations). More than 50% of the mutants tested still exhibited mitochondrial translation products (subunits I, II and III), suggesting that they carry a missense mutation, rather than a nonsense mutation which would normally have led to a truncated protein. Mutations in the COX1 gene were allocated to four different subregions corresponding to exons 4 and 8 or to groups of exons, exons 1, 2, 3 or exons 5, 6, 7. Seven missense monosubstitution mutations and two frameshift mutations were also identified. The amino acid changes of the missense mutations were located in the vicinity of the CuB-heme alpha 3 binuclear centre ligands.
...
PMID:Genetic screening in Saccharomyces cerevisiae for large numbers of mitochondrial point mutations which affect structure and function of catalytic subunits of cytochrome-c oxidase. 838 19

Phylogenetic relationships among eight species of the Drosophila buzzatii species complex (D. mulleri subgroup; D. repleta species group) and D. hamatofila were determined by sequencing the mitochondrial cytochrome oxidase subunit I, II, and III genes. The species examined included members of the martensis cluster (D. martensis, D. starmeri, D. venezolana), the buzzatii cluster (D. buzzatii, D. serido, D. borborema), and the stalkeri cluster (D. stalkeri, D. richardsoni). The molecular phylogeny was found to be congruent with the chromosomal inversion phylogeny. Analyzing the cytochrome oxidase subunits separately revealed that not all the subunits seem to have the same phylogenetic information content. Parameters are discussed that might explain these differences.
...
PMID:Phylogenetic utility of the mitochondrial cytochrome oxidase gene: molecular evolution of the Drosophila buzzatii species complex. 858 20


1 2 Next >>

---