Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Despite the extensive literature on the mechanism of action of the anticancer agent neocarzinostatin (NCS), the role of the protein moiety is still not clear. The model involving endocytosis of intact holo-NCS has been dismissed in favor of a theory proposing entry of free dissociated chromophore. However, the fact that the NCS protein has a certain affinity for cell membranes cannot be disregarded. In the present work the protein moiety has been modified by transformation of the carboxyl groups into isopropylamide groups. This modification resulted in a broad shift of the protein pI towards higher values, accompanied by a marked reduction of toxicity in vitro and reduced binding of protein to cells. Coincubation of modified NCS with inactive native apo-NCS led to restoration of the biological activity of native holo-NCS. It has been shown chromatographically that the modified NCS is capable of transferring active chromophore to native apo-NCS. The inactive form (apoprotein) of the charge-modified NCS, however, is capable of inhibiting the toxicity of the active form, as has been described for the corresponding native pair. Binding experiments with tritium-labeled proteins revealed that the modified protein has diminished affinity for membranes, in comparison with native NCS.
Mol Pharmacol 1994 Jun
PMID:The acidic groups of the neocarzinostatin protein play an important role in its biological activity. 802 19

The antihypertensive drug dihydralazine may, on rare occasions, cause immunoallergic hepatitis characterized by anti-cytochrome P450 (P450)1A2 autoantibodies. To understand the first steps leading to this immune reaction, we studied the covalent binding fo dihydralazine metabolites to microsomes from rat and human livers. Upon incubation with NADPH and microsomes, dihydralazine formed metabolites that reacted with heme (as evidenced by destruction of heme, formation of 445-nm light-absorbing complexes, and covalent binding of heme to P450 apoprotein) and covalently bound to microsomal proteins. Formation of these metabolites was shown (by NADPH dependence, induction by beta-naphthoflavone, and immunoinhibition by anti-P4501A antibodies) to be mediated by P4501A. Finally, these metabolites appeared to bind to P4501A2, which produced them. These results support the following scheme for the first steps of this autoimmune reaction: P4501A2 metabolizes dihydralazine into reactive metabolites that then bind to it, forming a neoantigen that triggers an immune response characterized by autoantibodies against P4501A2.
Mol Pharmacol 1994 Jun
PMID:Interactions of dihydralazine with cytochromes P4501A: a possible explanation for the appearance of anti-cytochrome P4501A2 autoantibodies. 802 22

The dynamic properties of the conformational states co-existing during the acid-induced unfolding of tuna apomyoglobin, a single tryptophan-containing protein, have been investigated simultaneously by frequency domain fluorometry. In the transition region, in the absence of salt, the tryptophanyl fluorescence emission arises from a bimodal lifetime distribution. The pH decrease causes a marked broadening of the short-lived distribution component whereas the other component, i.e. the long-lived one, remains unchanged and represented by a very narrow lifetime distribution whose width is similar to that of the native protein. The broadening of the short-lived distribution component observed on lowering the pH indicated that this component arises from fully unfolded molecules. This was further corroborated by acrylamide quenching studies at acidic pH. The collisional quenching rate constant of the short-lived distribution component, i.e. 8.9 x 10(9) M-1s-1, was found to be similar to that observed for a fully exposed residue. The long-lived distribution component was characterized by a lower collisional quenching rate constant, i.e. 2.3 x 10(9) M-1s-1. This value if compared to that determined for the native apoprotein at neutral pH, i.e. 4.0 x 10(8) M-1s-1, indicates that the native-like structure surviving the acid-induced transition possesses a large molecular flexibility.
J Mol Biol 1994 Aug 05
PMID:Unfolding pathway of apomyoglobin. Simultaneous characterization of acidic conformational states by frequency domain fluorometry. 805

CpG islands are always associated with the 5' end of housekeeping genes, covering their promoters and transcription start sites. CpG islands associated with genes of limited expression are less uniformly localized; the genes for apolipoprotein-E and -AI contain CpG islands corresponding to their last exons. As expected, the CpG island in the apo-AI gene is unmethylated in DNA from all tissues analyzed, expressing as well as non-expressing apolipoprotein-AI. In contrast, the apo-E CpG island is methylated in DNA from all tissues analyzed except sperm. The apo-E gene is transcribed in many tissues and is not repressed by this methylation. This establishes a functional difference between 5' and 3' CpG islands, because methylation of the former invariably leads to transcriptional repression. A similar methylation pattern was seen in the rat apo-E gene, which implies that this pattern probably was established before the divergence of rodents and primates. The numerous human apo-E alleles resulting from CpG to TpG/CpA mutations in the CpG island (i.e. deamination of methylated cytosine to thymine) suggest that this island is less protected from methylation in germ line than typical CpG islands.
Hum Mol Genet 1993 Jun
PMID:A methylated CpG island 3' in the apolipoprotein-E gene does not repress its transcription. 810 71

Four Nicotiana plumbaginifolia mutants exhibiting long hypocotyls and chlorotic cotyledons under white light, have been isolated from M2 seeds following mutagenesis with ethyl methane sulphonate. In each of these mutants, this partly etiolated in white light (pew) phenotype is due to a recessive nuclear mutation at a single locus. Complementation analysis indicates that three mutants, dap5, ems28 and ems3-6-34, belong to a single complementation group called pew1, while dap1 defines the pew2 locus. The mutants at pew1 contain normal levels of immunochemically detectable apoprotein of the phytochrome that is relatively abundant in etiolated seedlings, but are deficient in spectrophotometrically detectable phytochrome, whether seedlings are grown in darkness or light. Moreover, biliverdin, a precursor of the phytochrome chromophore, restores light-regulated responses in pew1 mutants and increases their level of photoreversible phytochrome when grown in darkness. These results indicate that the pew1 locus may be involved in chromophore biosynthesis. The mutant at the pew2 locus displays no photoreversible phytochrome in etiolated seedlings, but does contain normal levels of photoreversible phytochrome when grown in the light. Biliverdin had little effect on light-regulated responses in this mutant. In addition, biliverdin did not alter the level of phytochrome in etiolated seedlings. These observations lead us to propose that this mutant could be affected in the phyA gene itself. We have also obtained the homozygous double mutant at the pew1 and pew2 loci. This double mutant is lethal at an early stage of development, consistent with a critical role for phytochrome in early development of higher plants.
Mol Gen Genet 1994 Mar
PMID:Identification of two loci involved in phytochrome expression in Nicotiana plumbaginifolia and lethality of the corresponding double mutant. 812 13

The gene encoding Arabidopsis thaliana aspartate kinase (ATP:L-aspartate 4-phosphotransferase, EC 2.7.2.4) was isolated from genomic DNA libraries using the carrot ak-hsdh gene as the hybridizing probe. Two genomic libraries from different A. thaliana races were screened independently with the ak probe and the hsdh probe. Nucleotide sequences of the A. thaliana overlapping clones were determined and encompassed 2 kb upstream of the coding region and 300 bp downstream. The corresponding cDNA was isolated from a cDNA library made from poly(A)(+)-mRNA extracted from cell suspension cultures. Sequence comparison between the Arabidopsis gene product and an AK-HSDH bifunctional enzyme from carrot and from the Escherichia coli thrA and metL genes shows 80%, 37.5% and 31.4% amino acid sequence identity, respectively. The A. thaliana ak-hsdh gene is proposed to be the plant thrA homologue coding for the AK isozyme feedback inhibited by threonine. The gene is present in A. thaliana in single copy and functional as evidenced by hybridization analyses. The apoprotein-coding region is interrupted by 15 introns ranging from 78 to 134 bp. An upstream chloroplast-targeting sequence with low sequence similarity with the carrot transit peptide was identified. A signal sequence is proposed starting from a functional ATG initiation codon to the first exon of the apoprotein. Two additional introns were identified: one in the 5' non-coding leader sequence and the other in the putative chloroplast targeting sequence. 5' sequence analysis revealed the presence of several possible promoter elements as well as conserved regulatory motifs. Among these, an Opaque2 and a yeast GCN4-like recognition element might be relevant for such a gene coding for an enzyme limiting the carbon-flux entry to the biosynthesis of several essential amino acids. 3' sequence analysis showed the occurrence of two polyadenylation signals upstream of the polyadenylation site. This work is the first report of the molecular cloning of a plant ak-hsdh genomic sequence. It describes a promoter element that may bring new insights to the regulation of the biosynthesis of the aspartate family of amino acids.
Plant Mol Biol 1994 Mar
PMID:Molecular analysis of the aspartate kinase-homoserine dehydrogenase gene from Arabidopsis thaliana. 820 22

The effects of surfactant apoprotein A (SP-A) on the superoxide production of rat alveolar macrophages (AM) were studied. Superoxide production was measured by the ferricytochrome c reduction method. When AM were incubated with SP-A only during the measurement of superoxide production, superoxide production was not influenced by SP-A. However, when AM were preincubated with SP-A at a concentration of 1, 2, and 10 micrograms/ml, superoxide production by AM was significantly inhibited (P < 0.05, P < 0.01, P < 0.01, respectively). The superoxide production of AM stimulated by PMA was significantly inhibited by SP-A at a concentration of 1 microgram/ml (P < 0.01), and superoxide production stimulated by zymosan was also inhibited by SP-A at a concentration of 10 micrograms/ml (P < 0.05). Suppression of superoxide production of unstimulated and PMA-stimulated AM was significantly inhibited by anti-SP-A antibody. Superoxide generation by the xanthine and xanthine oxidase system was not affected by the presence of SP-A. Our results suggest that superoxide production of AM can be inhibited by SP-A and that this inhibitory effect on AM is due to a specific effect of SP-A. From these results, it is speculated that SP-A may have a protective role for oxidant injury by AM in the lung.
Am J Respir Cell Mol Biol 1993 Nov
PMID:Rat surfactant apoprotein A (SP-A) exhibits antioxidant effects on alveolar macrophages. 821 93

We have isolated cDNA and genomic clones for the potato (Solanum tuberosum) apoprotein 2 of the light harvesting complex of Photosystem I, designated Lhca3.St.1. The protein shows all characteristics of the family of chlorophyll a/b-binding proteins. Potato Lhca3.1 gene expression occurs predominantly in leaves, and is transcriptionally regulated by light. One gene copy is present per haploid genome. The sequence of the 5' upstream region was determined. Most boxes identified in the promoter sequences of genes whose expression is light-regulated recur in the Lhca3.St.1 sequence. Functional analyses of the Lhca3.St.1 promoter and two deletion derivatives in transgenic potato transformed with a promoter-GUS fusion show high promoter activity in leaves and other green parts of the plant, which depends on light. Activity is absent in roots and potato tubers. The 500 bp promoter fragment is as active as the full 2.0 kb sequence, showing that all regulatory elements are present on the smallest deletion derivative. In transgenic tobacco (Nicotiana tabacum) plants carrying the largest promoter derivative a similar distribution of activity is found. Promoter activity is not restricted to the phloem, but also prominent in the xylem of the young stem, which contrasts with promoters of other photosynthesis-associated genes.
Plant Mol Biol 1993 Nov
PMID:Activity of the promoter of the Lhca3.St.1 gene, encoding the potato apoprotein 2 of the light-harvesting complex of Photosystem I, in transgenic potato and tobacco plants. 821 93

Glucocorticoids increase surfactant phosphatidylcholine synthesis, in part, by stimulating the rate regulatory enzyme CTP:cholinephosphate cytidylyltransferase. This enzyme exists in mammalian lung cytosol as an active lipoprotein form (H-form) and an inactive apoprotein (L-form) species. We administered betamethasone to pregnant rats to examine the mechanisms for glucocorticoid stimulation of cytidylyltransferase activity in fetal lung. The hormone stimulated cytosolic activity threefold, and this effect was nearly abolished after lipid extraction. The addition of lipid extracts isolated from betamethasone-treated cytosolic preparations to L-form species increased enzyme activity to a greater extent than lipid extracts from control lungs. Further, the glucocorticoid increased the proportion of H-form activity from 34 to 55% of the total activity in the fetal lung cytosol. These changes were associated with a marked decrease in the activity of the L-form species. Analysis of the lipid composition of the H-form revealed that betamethasone increased the content of lipid activators, including phosphatidylglycerol and fatty acids. These observations provide evidence that glucocorticoid stimulation of CTP:cholinephosphate cytidylyltransferase in vivo is mediated by a conversion of the inactive form (L-form) to the active species (H-form). These studies further emphasize the critical role of lung lipids in mediating the glucocorticoid activation of this enzyme.
Am J Respir Cell Mol Biol 1994 Jan
PMID:Betamethasone activation of CTP:cholinephosphate cytidylyltransferase in vivo is lipid dependent. 829 80

Phosphorothioate pesticides, such as parathion (O,O-diethyl-O-4-nitrophenyl phosphorothioate), undergo enzymic oxidation to the active insecticidal agents that are the analogous organophosphorus compounds. In hepatic microsomal fractions, the NADPH-mediated conversion of parathion to paraoxon occurs with concomitant loss of cytochrome P450 (P450) and associated activities. In this study, the capacity of parathion to inactivate specific P450 enzymes was studied in rat hepatic microsomes. Parathion was a potent inhibitor of P450 3A2- and 2C11-mediated androst-4-ene-3,17-dione (androstenedione) 6 beta- and 16 alpha-hydroxylation (Ki values of 13 +/- 2 and 2.3 +/- 0.1 microM, respectively, and Km/Ki ratios of 1.4 +/- 0.2 and 11 +/- 1, respectively). After a 10-min preincubation between parathion and NADPH-supplemented microsomes, to inactivate P450 before androstenedione hydroxylation was carried out, the corresponding Km/Ki ratios were increased to 3.5 +/- 0.4 and 35 +/- 6, reflecting 2.5- and 3.2-fold enhancement of inhibition of P450 3A2- and 2C11-dependent activities. In contrast to these findings, P450 2A1/2-mediated androstenedione 7 alpha-hydroxylation was refractory to inhibition and P450 2C6-mediated progesterone 21-hydroxylation was inhibited but not inactivated by the pesticide. Further studies established that androstenedione 6 beta- and 16 alpha-hydroxylation pathways were inactivated with maximal half-times of 2.59 min and 1.72 min, respectively. Although the incubation of parathion (50 microM) with rat liver microsomes for 10 min led to a 16% decrease in P450 estimated spectrophotometrically, immunoblot analysis revealed no change in the microsomal content of P450 2C11 apoprotein. Finally, NADPH-mediated metabolism of parathion to paraoxon (by desulfuration) and 4-nitrophenol (by oxidative cleavage of the phosphorothioate ester) occurred efficiently in microsomes (4.32 and 4.35 nmol/min/mg of protein, respectively). P450 loss was estimated under the same incubation conditions and, thus, 210 parathion molecules were oxidized for each molecule of holo-P450 lost. These findings establish that parathion is a potent inhibitor and inactivator of the principal constitutive P450s, 3A2 and 2C11, in rat liver, whereas the P450s 2A1 and 2A2 are refractory to either inhibition or inactivation. Another major constitutive enzyme, P450 2C6, is inhibited effectively by parathion but does not appear to be subject to inactivation.
Mol Pharmacol 1993 Jun
PMID:Inhibition and inactivation of constitutive cytochromes P450 in rat liver by parathion. 831 22


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>