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Query: UNIPROT:P06889 (Mol)
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The gene rpoA, encoding a protein homologous to the alpha subunit of RNA polymerase from Escherichia coli has been located in pea chloroplast DNA downstream of the petD gene for subunit IV of the cytochrome b-f complex. Nucleotide sequence analysis has revealed that rpoA encodes a polypeptide of 334 amino acid residues with a molecular weight of 38916. Northern blot analysis has shown that rpoA is co-transcribed with the gene for ribosomal protein S11. A lacZ-rpoA gene-fusion has been constructed and expressed in E. coli. Antibodies raised against the fusion protein have been employed to demonstrate the synthesis of the rpoA gene product in isolated pea chloroplasts. Western blot analysis using these antibodies and antibodies against the RNA polymerase core enzyme from the cyanobacterium, Anabaena 7120, has revealed the presence of the gene product in a crude RNA polymerase preparation from pea chloroplasts.
Mol Gen Genet 1989 May
PMID:The plastid rpoA gene encoding a protein homologous to the bacterial RNA polymerase alpha subunit is expressed in pea chloroplasts. 267 52

The terminal intron (bI2) of the yeast mitochondrial cytochrome b gene is a group I intron capable of self-splicing in vitro at high concentrations of Mg2+. Excision of bI2 in vivo, however, requires a protein encoded by the nuclear gene CBP2. The CBP2 protein has been partially purified from wild-type yeast mitochondria and shown to promote splicing at physiological concentrations of Mg2+. The self-splicing and protein-dependent splicing reactions utilized a guanosine nucleoside cofactor, the hallmark of group I intron self-splicing reactions. Furthermore, mutations that abolished the autocatalytic activity of bI2 also blocked protein-dependent splicing. These results indicated that protein-dependent excision of bI2 is an RNA-catalyzed process involving the same two-step transesterification mechanism responsible for self-splicing of group I introns. We propose that the CBP2 protein binds to the bI2 precursor, thereby stabilizing the catalytically active structure of the RNA. The same or a similar RNA structure is probably induced by high concentrations of Mg2+ in the absence of protein. Binding of the CBP2 protein to the unspliced precursor was supported by the observation that the protein-dependent reaction was saturable by the wild-type precursor. Protein-dependent splicing was competitively inhibited by excised bI2 and by a splicing-defective precursor with a mutation in the 5' exon near the splice site but not by a splicing-defective precursor with a mutation in the core structure. Binding of the CBP2 protein to the precursor RNA had an effect on the 5' splice site helix, as evidenced by suppression of the interaction of an exogenous dinucleotide with the internal guide sequence.
Mol Cell Biol 1989 Dec
PMID:CBP2 protein promotes in vitro excision of a yeast mitochondrial group I intron. 268 64

We have identified a gene that encodes the polypeptide cytochrome b in the avian malarial parasite Plasmodium gallinaceum. The gene containing the open reading frame was found to be located on a 6.2-kilobase multimeric extrachromosomal element. The amino acid translation from this gene demonstrated significant similarities to cytochrome b sequences from yeast, mammal, and fungus genomes. We present evidence that the P. gallinaceum cytochrome b transcript is part of a larger primary transcript from the element that is subsequently processed. The message for P. gallinaceum cytochrome b was found to be 1.2 kilobases in size. This is the first report identifying a mitochondrial nucleic acid sequence in malaria-causing organisms and suggests that a functional cytochrome system may exist in these parasites.
Mol Cell Biol 1989 Sep
PMID:Sequence identification of cytochrome b in Plasmodium gallinaceum. 277 60

We have identified a conserved, repeated, and highly transcribed DNA element from the avian malarial parasite Plasmodium gallinaceum. The element produced multiple transcripts in both zygotes and asexual blood stages of this parasite. It was found to be highly conserved in all of five malarial species tested and hybridized at reduced stringency to other members of the phylum Apicomplexa, including the genera Babesia, Eimeria, Toxoplasma, and Theileria. The copy number of the element was about 15, and it had a circularly permuted restriction map with a repeat unit length of about 6.2 kilobases. It could be separated from the main genomic DNA by using sucrose gradients and agarose gels, and it migrated separately from the recognized Plasmodium chromosomes on pulse-field gels. In the accompanying paper (S. M. Aldritt, J. T. Joseph, and D. F. Wirth, Mol. Cell. Biol. 9:3614-3620, 1989), evidence is presented that element contains the mitochondrial genes for the protein cytochrome b and a fragment of the large rRNA. We postulate that this element is an episome in the mitochondria of the obligate parasites belonging to the phylum Apicomplexa.
Mol Cell Biol 1989 Sep
PMID:Characterization of a conserved extrachromosomal element isolated from the avian malarial parasite Plasmodium gallinaceum. 277 61

The structural genes for the Rieske Fe-S protein (petA), cytochrome b (petB) and cytochrome c1 (petC) subunits of the ubiquinol:cytochrome c2 oxidoreductase (bc1 complex) of Rhodopseudomonas capsulata have been cloned by complementation, using a mutant defective in this complex. The location of these genes on the obtained plasmid, pR14A, was determined using synthetic mixed oligonucleotide probes corresponding to highly conserved amino acid sequences of these proteins from various organisms. Their correct identity was established by partial sequencing. The petA, petB and petC genes were found to lie close to each other in this order, spanning two adjacent EcoRI fragments of 2.7 X 10(3) and 1.3 X 10(3) base-pairs, respectively. An insertion-deletion mutation, covering most of petB and all of petC and an insertion mutation, located in petB were constructed in vitro and were introduced into the chromosome of an otherwise wild-type strain by gene transfer agent-mediated genetic crosses. The bc-1 mutants obtained were defective in photosynthesis but, as expected, they could grow by respiration because of a branched respiratory pathway. Therefore, in R. capsulata a functional bc1 complex is essential in vivo for photosynthesis but not for respiration. Further, in the respiratory pathway the branch point must be before the bc1 complex, most likely at the quinone pool. These mutants were also proficient in anaerobic growth in the presence of dimethylsulfoxide, indicating that a functional bc1 complex is not required for this pathway. Several other insertions and deletions, located outside of the pet gene cluster, were also constructed. The ability of these latter mutants to grow photosynthetically suggested that no other gene essential for photosynthesis is located in the proximity of the pet cluster. The plasmid pR14A was shown to complement in trans the bc-1 insertion or insertion-deletion mutants, indicating that the pet genes were expressed in R. capsulata. Cross-hybridization experiments showed that the pet cluster was quite distinct from other known genes involved in photosynthesis.
J Mol Biol 1987 May 05
PMID:Isolation of the structural genes for the Rieske Fe-S protein, cytochrome b and cytochrome c1 all components of the ubiquinol: cytochrome c2 oxidoreductase complex of Rhodopseudomonas capsulata. 282 Dec 66

The nucleotide sequence of the pet operon of Rhodopseudomonas capsulata strain SB1003 has been determined. This operon consists of the petA, petB and petC genes, which encode the Rieske Fe-S protein, cytochrome b and cytochrome c1, respectively, all components of the ubiquinol-cytochrome c2 oxidoreductase. The deduced amino acid sequences of the pet genes show homology to the corresponding proteins from other organisms, and particularly high homologies (over 90% for amino acid and nucleotide sequences) to the previously described fbc operon from a strain previously identified as Rhodopseudomonas spheroides GA. The amino acid sequences of the pet proteins are discussed with reference to the structure and function of the ubiquinol-cytochrome c2 oxidoreductase.
J Mol Biol 1987 May 05
PMID:Primary structure of the bc1 complex of Rhodopseudomonas capsulata. Nucleotide sequence of the pet operon encoding the Rieske cytochrome b, and cytochrome c1 apoproteins. 282 Dec 68

Detailed comparison of the 'Rhodopseudomonas sphaeroides GA' strain used by Gabellini et al. (1985) with genuine R. sphaeroides and R. capsulata strains indicated that the previously reported fbc operon of R. sphaeroides (Gabellini and Sebald, 1986) encoding the structural genes for the Rieske Fe-S protein, cytochrome b and cytochrome c1 subunits of the ubiquinol:cytochrome c2 oxidoreductase, is not from R. sphaeroides, but is rather from a strain of R. capsulata. Consequently, the genuine bc1 genes from R. sphaeroides were cloned using corresponding R. capsulata genes as probes, and a partial nucleotide sequence for the Rieske Fe-S protein of R. sphaeroides was determined and compared with that of R. capsulata.
J Mol Biol 1987 May 05
PMID:fbc operon, encoding the Rieske Fe-S protein cytochrome b, and cytochrome c1 apoproteins previously described from Rhodopseudomonas sphaeroides, is from Rhodopseudomonas capsulata. 282 Dec 72

A series of mouse lines with increased resistance to respiratory inhibitors which block electron transport through the protonmotive cytochrome b of complex III have been isolated in this laboratory. We describe here the isolation of a mutant with increased resistance to HQNO (2-n-heptyl-4-hydroxyquinoline-N-oxide) whose phenotype is due to a nuclear mutation. At the cellular level, there is a severe reduction in respiration with the residual oxygen consumption being resistant to inhibitors of both ubiquinol-cytochrome c oxidoreductase and cytochrome oxidase. At the mitochondrial level, there was a severe derangement in NADH oxidase activity. Electron transport through the succinate oxidase span of the respiratory chain and its coupling to oxidative phosphorylation are also reduced in this nuclear mutant but not to the same extent. It is concluded that the primary defect in the mutant lies within a nuclear gene encoding a component of complex I (NADH-ubiquinol oxidoreductase). In addition, further biochemical characterization of the mitochondrially inherited inhibitor-resistant mutants has demonstrated that they also show significant reductions in the efficiency of energy transduction and in the rate of cytochrome b electron transport.
Somat Cell Mol Genet 1987 Sep
PMID:Characterization of mouse nuclear and mitochondrial mutants with increased resistance to cytochrome b inhibitors. 282 32

The sequence of the 16,019 nucleotide-pair mitochondrial DNA (mtDNA) molecule of Drosophila yakuba is presented. This molecule contains the genes for two rRNAs, 22 tRNAs, six identified proteins [cytochrome b, cytochrome c oxidase subunits I, II, and III (COI-III), and ATPase subunits 6 and 8] and seven presumptive proteins (URF1-6 and URF4L). Replication originates within a region of 1077 nucleotides that is 92.8% A + T and lacks any open reading frame larger than 123 nucleotides. An equivalent to the sequence found in all mammalian mtCDNAs that is associated with initiation of second-strand DNA synthesis is not present in D. yakuba mtDNA. Introns are absent from D. yakuba mitochondrial genes and there are few (0-31) intergenic nucleotides. The genes found in D. yakuba and mammalian mtDNAs are the same, but there are differences in their arrangement and in the relative proportions of the complementary strands of the molecule that serve as templates for transcription. Although the D. yakuba small and large mitochondrial rRNA genes are exceptionally low in G and C and are shorter than any other metazoan rRNA genes reported, they can be folded into secondary structures remarkably similar to the secondary structures proposed for mammalian mitochondrial rRNAs. D. yakuba mitochondrial tRNA genes, like their mammalian counterparts, are more variable in sequence than nonorganelle tRNAs. In mitochondrial protein genes ATG, ATT, ATA, and in one case (COI) ATAA appear to be used as translation initiation codons. The only termination codon found in these genes is TAA. In the D. yakuba mitochondrial genetic code, AGA, ATA, and TGA specify serine, isoleucine, and tryptophan, respectively. Fifty-nine types of sense condon are used in the D. yakuba mitochondrial protein genes, but 93.8% of all codons end in A or T. Codon-anticodon interactions may include both G-A and C-A pairing in the wobble position. Evidence is summarized that supports the hypothesis that A and T nucleotides are favored at all locations in the D. yakuba mtDNA molecule where these nucleotides are compatible with function.
J Mol Evol 1985
PMID:The mitochondrial DNA molecular of Drosophila yakuba: nucleotide sequence, gene organization, and genetic code. 300 25

DNA clones have been isolated that span the complete mitochondrial (mt) genome of the dolphin, Cephalorhynchus commersonii. Hybridization experiments with purified primate mtDNA probes have established that there is close resemblance in the general organization of the dolphin mt genome and the terrestrial mammalian mt genomes. Sequences covering 2381 bp of the dolphin mt genome from the major noncoding region, three tRNA genes, and parts of the genes encoding cytochrome b, NADH dehydrogenase subunit 3 (ND3), and 16S rRNA have been compared with corresponding regions from other mammalian genomes. There is a general tendency throughout the sequenced regions for greater similarity between dolphin and bovine mt genomes than between dolphin and rodent or human mt genomes.
J Mol Evol
PMID:Molecular characterization of a cloned dolphin mitochondrial genome. 314 40


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