PubMed Health⌕ Search

Biomedical subjects

S Numa

Publications and source records attributed to S Numa.

At least 109 records · Page 6Linked to original sources
PubMed1981

Isolation and characterization of the bovine corticotropin/beta-lipotropin precursor gene.

The entire bovine corticotropin/beta-lipotropin precursor gene has been isolated as a set of overlapping genomic DNA fragments which extend over a length of approximately 17000 base pairs. Restriction mapping of the cloned DNA fragments and nucleotide sequence analysis of the whole mRNA-coding segments and their surrounding regions have established that the corticotropin/beta-lipotropin precursor gene is approximately 7300-base-pairs long and contains two intervening sequences; one with an approximate length of 4000 base pairs is located within the segment encoding the 5'-untranslated region of the mRNA, and the other with an approximate length of 220 base pairs interrupts the protein-coding sequence near the signal peptide region. Sequence analysis of more than 200 base pairs preceding the proximal end of the corticotropin/beta-lipotropin precursor gene has revealed a 'Hogness box' and a variant of the model sequence d(G-G-TC-C-A-A-T-C-T) as well as palindrome structures as observed in other eukaryotic genes. Furthermore, some sequence similarities in the 5'-flanking region are found between the corticotropin/beta-lipotropin precursor gene and the mouse alpha-globin and beta-globin genes, all of which are negatively regulated by glucocorticoids. At least four homologous repetitive sequences are distributed at 3000-5000-base-pair distances in the corticotropin/beta-lipotropin precursor gene region; two such sequences are located in the 5'-flanking region, and one within each intervening sequence. Blot hybridization analysis of bovine pituitary nuclear RNA has indicated that the entire corticotropin/beta-lipotropin precursor gene is transcribed into a primary hnRNA product, which is then spliced to form the mature mRNA.

Adrenocorticotropic Hormone↗
PubMed1980

The protein-coding sequence of the bovine ACTH-beta-LPH precursor gene is split near the signal peptide region.

The pituitary hormones corticotropin (ACTH) and beta-lipotropin (beta-LPH) are formed from a large common precursor. Recently, we have elucidated the whole primary structure of the bovine ACTH-beta-LPH precursor (designated alternatively as preproopiocortin) by determining the nucleotide sequence of cloned DNA complementary to the mRNA coding for the precursor protein. The amino acid sequence assigned has disclosed a characteristic repetitive structure of the ACTH-beta-LPH precursor. The repetitive units of the precursor protein each contain a melanotropin (MSH) sequence (alpha-, beta- or gamma-MSH) as well as other peptide components such as beta-endorphin and corticotropin-like intermediate lobe peptide (CLIP). The repetitive units as well as their peptide components are each bounded by paired basic amino acid residues, which apparently represent the sites of proteolytic processing. Several studies have confirmed the translational initiation site and protein structure assigned (see also ref. 11 and refs therein). In view of the recent knowledge about the organization of eukaryotic genes (see refs 12, 13 for reviews), it would be of particular interest to investigate the relationship between the repetitive structure of the ACTH-beta-LPH precursor containing different functional components and the arrangement of the protein-coding sequence in its gene. We have now isolated and characterized bovine genomic DNA fragments encoding this precursor protein and have demonstrated that the protein sequence is encoded by two non-consecutive DNA segments. An intron (intervening sequence) of approximately 2.2 kilobase pairs separates the smaller exon (mRNA-coding sequence), which contains the gene sequence encoding the signal peptide, from the larger exon, which contains the gene sequence for most of the protein structure, including the known biologically active component peptides.

Adrenocorticotropic Hormone↗
PubMed1980

Fatty acid-requiring mutant of Saccharomyces cerevisiae defective in acetyl-CoA carboxylase.

The isolation and biochemical properties of a Saccharomyces cerevisiae mutant (acc1-167) defective in acetyl-CoA carboxylase [acetyl-CoA:carbon-dioxide ligase (ADP forming), EC 6.4.1.2] activity are described. The mutant is deficient in de novo biosynthesis of long-chain fatty acids and specifically requires a saturated fatty acid of chain length 14-16 C atoms for growth. Fatty acid synthetase levels were normal, but the acetyl-CoA carboxylase specific activity of the purified enzyme was reduced to approximately 5% compared to wild-type yeast. Upon sodium dodecyl sulfate/polyacrylamide gel electrophoresis the purified mutant enzyme migrated as a single band and was essentially indistinguishable from the wild-type enzyme. The study of acetyl-CoA carboxylase partial activities revealed that the biotin incorporation capacity and the transcarboxylase partial activity were unaffected whereas the biotin carboxylase component enzyme exhibited less than 10% of wild-type specific activity. This biotin carboxylase mutational deficiency could be ascribed to a more than 90% reduction of Vmax and to a comparable increase in the Km value for ATP, which was accompanied by an increased requirement for Mg2+. It is concluded that acc1-167 contains a structural gene mutation in the biotin carboxylase domain of acetyl-CoA carboxylase.

Acetyl-CoA Carboxylase↗
PubMed1980

Cell-free translation and regulation of Candida lipolytica acetyl-coenzyme-A carboxylase messenger RNA.

Messenger RNA from Candida lipolytica directs the synthesis of complete acetyl-coenzyme-A carboxylase in the mRNA-dependent reticulocyte lysate cell-free translation system. The identity of the translation product is evidenced by the following results: first, it is immunoprecipitated with antibody to acetyl-CoA carboxylase and competes with authentic acetyl-CoA carboxylase for binding to the antibody; secondly, it co-migrates with authentic acetyl-CoA carboxylase (Mr 230000) upon dodecylsulfate/polyacrylamide gel electrophoresis; finally, the peptide fragments formed by its partial proteolysis with papain or alpha-chymotrypsin are identical with those formed from authentic acetyl-CoA carboxylase. With the use of this assay system, it has been demonstrated that the level of acetyl-CoA carboxylase mRNA activity in C. lipolytica cells decreases with increasing concentrations of oleic acid in culture medium and that the changes in the mRNA activity parallel those in the cellular level of acetyl-CoA carboxylase. This finding, in conjunction with our previous study, indicates that the diminished synthesis of acetyl-CoA carboxylase in cells grown in the presence of fatty acid is due to a reduced level of the mRNA coding for the enzyme.

Acetyl-CoA Carboxylase↗
PubMed1979

Nucleotide sequence of cloned cDNA for bovine corticotropin-beta-lipotropin precursor.

The nucleotide sequence of a 1,091-base pair cloned cDNA insert encoding bovine corticotropin-beta-lipotropin precursor mRNA is reported. The corresponding amino acid sequence indicates that the precursor protein consists of repetitive units and includes a third melanotropin sequence in its cryptic portion. Pairs of lysine and arginine residues separate the component peptides of the precursor.

Adrenocorticotropic Hormone↗
PubMed1979

Purification and characterization of the messenger RNA coding for bovine corticotropin/beta-lipotropin precursor.

The mRNA coding for the common precursor of corticotropin and beta-lipotropin has been purified to homogeneity from neurointermediate lobes of bovine pituitaries. The homogeneity of the mRNA preparation is evidenced by analysis of its translation product, electrophoresis on polyacrylamide gel in the presence of formamide and analysis of the kinetics of hybridization with its cDNA. The purification procedure involves the isolation of RNA from membrane-bound polysomes, chromatography on oligo(dT)-cellulose and on poly(U)-Sepharose and sucrose density gradient centrifugation. The mRNA has a molecular weight of approximately 450000, equivalent to approximately 1360 nucleotides in length, and contains a polyadenylate sequence with an average length of 68 nucleotides. The size of the mRNA is sufficiently large to encode the corticotropin/beta-lipotropin precursor.

Adrenocorticotropic Hormone↗
PubMed1979

Acyl-coenzyme-A synthetase I from Candida lipolytica. Purification, properties and immunochemical studies.

Acyl-coenzyme-A synthetase I from Candida lipolytica has been purified to homogeneity as evidenced by polyacrylamide gel electrophoresis in the presence and absence of dodecylsulfate as well as by Ouchterlony double-diffusion analysis. The purification procedure involves resolution of cellular particles with Triton X-100 and chromatography on phosphocellulose, Blue-Sepharose and Sephadex G-100. The purified enzyme exhibits a specific activity of 20--24 U/mg protein at 25 degree C, which is about 100-fold higher than those of long-chain acyl-CoA synthetases hitherto reported. The molecular weight of the enzyme has been estimated by polyacrylamide gel electrophoresis in the presence of dodecylsulfate to be approximately 84 000. The enzyme is specific for fatty acids with 14--18 carbon atoms regardless of the degree of unsaturation. Studies with the use of specific antibody to acyl-CoA synthetase I have indicated that this enzyme is immunochemically distinguishable from acyl-CoA synthetase II.

Candida↗
PubMed1979

Distribution of the messenger RNA coding for the common precursor of corticotropin and beta-lipotropin within the bovine pituitary.

The distribution of the mRNA coding for the common precursor of corticotropin and beta-lipotropin among different parts of the bovine pituitary has been investigated by quantifying the mRNA activity with the use of a cell-free protein-synthesizing system. The results obtained have demonstrated that this mRNA activity is located both in the anterior lobe and in the intermediate lobe, while it is essentially not detectable in the neural lobe nor in the stalk. The structural identity of the translation products of corticotropin/beta-lipotropin mRNA from the anterior and from the intermediate lobe has been indicated by their molecular weight as well as by the electrophoretic patterns of the peptide fragments formed from them upon partial enzymatic proteolysis or upon cyanogen bromide cleavage. The specific activity of corticotropin/beta-lipotropin mRNA in the intermediate lobe is about 20-fold higher than that in the anterior lobe, and the total activity of this mRNA in the former is about 2-fold higher than that in the latter. In the intermediate lobe, the translation product of corticotropin/beta-lipotropin mRNA amounts to almost one-third of the products encoded by total translatable mRNA. These results indicate that corticotropin/beta-lipotropin mRNA represents a major mRNA species in intermediate lobe of the pituitary, thus suggesting that this lobe may perform a highly specialized function in producing a large amount of the common precursor of corticotropin and beta-lipotropin.

Adrenocorticotropic Hormone↗
PubMed1979

Involvement of long-chain acyl coenzyme A for lipid synthesis in repression of acetyl-coenzyme A carboxylase in Candida lipolytica.

Mutant strains of Candida lipolytica defective in acyl-CoA synthetase II [acid:CoA ligase (AMP-forming), EC 6.2.1.3] have been isolated. The mutants fail to grow on fatty acid as a sole carbon source but are capable of incorporating exogenous fatty acid into cellular lipids. This observation, together with our previous finding that mutant strains defective in acyl-CoA synthetase I cannot incorporate exogenous fatty acid into cellular lipids but are able to degrade fatty acid via beta-oxidation, indicates the presence of two functionally distinct long-chain acyl-CoA pools in the cell--i.e., one for lipid synthesis and the other for beta-oxidation. Unlike the wild-type and the revertant strains as well as the mutants lacking acyl-CoA synthetase II, the mutants defective in acyl-CoA synthetase I do not exhibit the repression of acetyl-CoA carboxylase [acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] by exogenous fatty acid. Measurement of the two long-chain acyl-CoA pools with the aid of appropriate mutant strains has indicated that the long-chain acyl-CoA to be utilized for lipid synthesis, but not that to be degraded via beta-oxidation, is involved in the repression of acetyl-CoA carboxylase.

Acetyl-CoA Carboxylase↗
PubMed1978

Subcellular localization of two long-chain acyl-coenzyme-A synthetases in Candida lipolytica.

Studies have been made on the subcellular localization of two long-chain acyl-coenzyme-A synthetases as well as glycerolphosphate acyltransferase and the acyl-CoA-oxidizing system in Candida lipolytica grown on oleic acid. Acyl-CoA synthetase I is distributed among different subcellular fractions, including microsomes and mitochondria where glycerolphosphate acyltransferase is located. On the other hand, acyl-CoA synthetase II is localized in microbodies where the acyl-CoA-oxidizing system is located. These results support our previous conclusion that acyl-CoA synthetase I is responsible for the production of acyl-CoA to be utilized for the synthesis of cellular lipids, while acyl-CoA synthetase II provides acyl-CoA that is exclusively degraded via beta-oxidation.

Candida↗