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)

RNA from oocysts of Eimeria tenella was purified into poly(A)--RNA and poly(A)+-RNA fractions with affinity chromatography on oligo(dT)-cellulose. Gel electrophoresis, under denaturing conditions of the poly(A)--RNA fraction revealed two major RNAs with molecular weights of 1.27 and 0.65 X 10(6). The values for these components not only represent the ribosomal RNAs of this species; but they also resemble the molecular sizes of the non-mRNAs of many other lower eukaryotes. In vitro translation assays with a cell-free wheat germ system showed that the level of translatable mRNA in the poly(A)--RNA fraction was negligible. Virtually all the translatable mRNA in E. tenella was polyadenylated, that is, it contained poly(A)-tracts with more than 15 adenylate residues. Consequently some of the key components of the protein translational machinery of this organism are eukaryotic in nature.
Mol Biochem Parasitol 1981 Jul
PMID:Ribosomal and translatable messenger RNA of Eimeria tenella. 616 61

Praziquantel (PZ) at concentrations down to 5 x 10(-8) M induced a rapid contraction of Hymenolepis diminuta musculature. This effect was accompanied by a strong inhibition of 45Ca2+ incorporation which showed some dependence on Ca2+ concentration. Ca2+ efflux experiments showed that PZ markedly stimulated the release of Ca2+ from tapeworms preloaded with 45Ca2+, with the effluxed Ca2+ being derived from a small fast pool and a larger slow pool. This stimulatory effect appeared., like PZ-induced muscle contraction, to be independent of external Ca2+. By carrying out 45Ca2+ exchange experiments under near equilibrium conditions and atomic absorption spectroscopy it could be demonstrated that PZ resulted in a net excretion of endogenous Ca2+. In PZ-induced contracted worms adenylate nucleotide levels and the adenylate energy charge were not significantly different from those of untreated control worms. Also, PZ had no effect on Ca2+-stimulated ATPase activity of the tapeworm's tegumental brush border. Nor did the drug alter the activities of Ca2+-ATPases in whole homogenates of worms or mitochondria, microsomal or soluble fractions. Although the mechanism of PZ-induced changes in Ca2+ transport was not elucidated, it is suggested that the sustained release of endogenous Ca2+ may affect the sequence of excitation-contraction coupling and that such interference may cause the observed massive contraction of the tapeworm's musculature.
Mol Biochem Parasitol 1982 May
PMID:The effect of praziquantel on calcium in Hymenolepis diminuta. 621 63

Hexokinase (ATP: hexose 6-phosphotransferase, E.C.2.7.1.1) and phosphofructokinase (ATP:fructose-6-phosphate 1-phosphotransferase, E.C.2.7.1.11), two key regulatory enzymes of the glycolytic pathway in vertebrate cells, have been isolated and partially purified from Trypanosoma (Schizotrypanum) cruzi epimastigotes. Both enzymes are associated with particles sedimentable at 105 000 X gav for 1 h and have a high degree of latency; they can be solubilized by sonication. Hexokinase catalyses the phosphorylation of a series of monosaccharides at the following relative rates: D-glucose (100) congruent to D-fructose (97) greater than 2-deoxy-D-glucose (72) congruent to mannose (69) greater than 2-amino-D-glucose (63) greater than 3-O-methyl-D-glucose (21). Very little or no phosphorylating activity was found for D-galactose, N-acetyl-2-amino-D-glucose or 1-alpha-methyl-D-glucose. D-Glucose phosphorylation at fixed ATP concentration follows simple Michaelis-Menten kinetics with Km = 40 microM and Vmax = 440 nmol min-1 mg-1 protein. D-Mannose, 2-deoxy-D-glucose and N-acetyl-2-amino-D-glucose act as competitive inhibitors of glucose phosphorylation, suggesting a single kinase. Mg2+-ATP is the preferred phosphoryl donor, ITP and GTP being much less effective. T. cruzi hexokinase is not inhibited by D-glucose 6-phosphate, or by any of the following compounds (2 mM):D-fructose 6-phosphate, D-fructose 1,6-diphosphate, D-glucose 1,6-diphosphate, phosphoenol pyruvate, L-malate and citrate. Phosphofructokinase displays simple Michaelis-Menten kinetics with no evidence of sigmoidicity with respect to D-fructose 6-phosphate at all ATP concentrations tested, giving a Km of 1.31 mM and Vmax = 400 nmol min-1 mg-1 protein at optimal ATP levels. With respect to ATP, the enzyme exhibits Michaelis-Menten kinetics at low concentration (less than 1 mM) of the substrate (Km = 40 microM at 5 mM MgCl2, pH 7.4). A moderate inhibition is observed at high ATP levels (70% of maximal activity at 2 mM). GTP can substitute for ATP as the phosphoryl donor (Km = 79 microM under the same conditions), but produces only very small inhibitory effects at high concentrations. 5'-AMP activates the enzyme by decreasing its Km with respect to D-fructose 6-phosphate without affecting Vm. Other well-known regulators of the activity of this enzyme in procaryote and vertebrate systems such as citrate, phosphoenol pyruvate, ammonium and phosphate ions have no effect in T. cruzi.
Mol Biochem Parasitol 1984 Apr
PMID:Regulation of energy metabolism in Trypanosoma (Schizotrypanum) cruzi epimastigotes. I. Hexokinase and phosphofructokinase. 623 52

The ability of LH to stimulate, in vitro, adenylate cylcase activity and testosterone secretion was studied in foetal rat testes after prelabelling with [14C]adenine. As little as 0.1 ng/ml LH produced significant synthesis of cyclic AMP and testosterone secretion. Increase of cyclic AMP production was observed as early as 1 min after addition of LH (100 ng/ml), preceding the rise in testosterone synthesis and secretion. FSH and prolactin were not effective. LH-stimulation of cyclic AMP and testosterone production appeared concomitantly in rat foetal testes on day 15 of gestation and reached a maximum on day 18. Immature testes (14 days) developed functional receptors when cultured in a medium devoid of hormone. The results of the present study suggest that cyclic AMP mediates the effect of LH on steroidogenesis in foetal testes and that the differentiation of functional receptors occurs at the same time as the capacity for testosterone synthesis.
Mol Cell Endocrinol 1980 May
PMID:Acquisition of sensitivity to LH in relation to foetal development. Stimulation of cyclic AMP and testosterone production in the rat testis. 624 25

Exposure of the oestrogen-dominated rat myometrium to either isoproterenol or PGE2 resulted in a rapid but transient accumulation of cyclic AMP, with a progressive loss of responsiveness to the corresponding agonist. Induction of refractoriness was a time- and dose-related phenomenon. In the earliest time, desensitization was agonist-specific but was followed, with continued exposure, by a cross desensitization between isoproterenol and PGE2 and vice versa. Differential time courses for development and reversal of specific and heterologous refractoriness indicate at least 2 different processes for the 2 phenomena, the non-specific type being possibly mediated by cyclic AMP. Exposure to isoproterenol or PGE2 also caused an attenuated cyclic AMP response to prostacyclin (PGI2). Kinetics for PGE2-induced desensitization to PGI2 were comparable to that of an agonist-specific refractoriness, indicating that PGE2 and PGI2 may share common receptor sites. PGF2 alpha, PGD2 and 6-keto PGF1 alpha, which contract the myometrium but are ineffective on adenylate-cyclase activity, did not promote cyclic AMP refractoriness to PGE2, PGI2 or isoproterenol. Isoproterenol also caused refractoriness to its own relaxing activity, whereas PGE2 did not affect isoproterenol-induced relaxation despite a marked attenuation of the beta-adrenergic response to cyclic AMP. These results provide further evidence for the non-exclusive role of cyclic AMP in mediating uterine relaxation.
Mol Cell Endocrinol 1980 Oct
PMID:Modulation of cyclic AMP content of the rat myometrium: desensitization to isoproterenol, PGE2 and prostacyclin. 625 20

Intracellular content of cyclic 3',5'-adenosine monophosphate was determined in several strains of Trypanosoma brucei brucei during their growth in rats. In non-relapsing infections with the cloned monomorphic strain 110M and with the cloned pleomorphic strain YTatl, the amount of cyclic AMP per 10(9) trypanosomes increased from 30 to over 90 pmol as the parasitemia increased from patency to over 10(9) organisms per ml. This increase was not observed during non-relapsing infections with strain 427. During infections with strain YTatl in both immunocompetent and lethally X-irradiated rats, cyclic AMP content of the parasite increased from 20--20 pmol per 10(9) cells early in logarithmic growth to 65--70 pmol per 10(9) cells at peak parasitemia, then decreased as the transition to intermediate and short stumpy forms commenced. At crisis, basal levels were reestablished when log slender forms were the lowest percentage of the total population and intermediate and short stumpy forms predominated, suggesting a correlation between morphologic type and level of cyclic AMP per cell during fluctuations in parasitemia. Increases in intracellular cyclic AMP were measured during in vitro incubation of the parasite in medium containing potential effectors of the trypanosome cyclic AMP system. Sodium fluoride, adenosine and methyl xanthines stimulated increases in cyclic AMP content while isoproterenol, prostaglandin E1, serotonin, histamine and several trypanocidal drugs were ineffective. The results are discussed in terms of the possible regulatory role of cyclic AMP in differentiation of trypanosomes.
Mol Biochem Parasitol 1981 May
PMID:Cyclic 3',5'-adenosine monophosphate levels during the developmental cycle of Trypanosoma brucei brucei in the rat. 626 73

The interactions of Ni(II) cation with a representative suite of purine bases and the respective nucleosides and nucleotides have been studied by ultraviolet difference spectroscopy. Apparent association constants, Kapp, were determined for each system at pH 7.0, using computer linear regression coupled with an iteration technique. The specificity of binding of Ni2+ for the purine nucleotides studied at pH 7.0 was 5'-GMP greater than 5'-IMP greater than 5'-AMP; a similar ordering was also found for the respective nucleosides and bases. In this study binding was not observed for the suite of pyramidines used, although a Ni2+ - cytidine complex has been observed (Fiskin and Beer, 1965). It was also found that Ni2+ bound more strongly to the purine 5'-nucleotides than to the respective nucleosides and bases. These trends are explained in terms of metal-ligand bonds and available bonding positions on the ligands. A role for metal-ion-nucleotide types of complexes is suggested in the processes that might have given rise to the origin of life.
J Mol Evol 1982
PMID:Binding of nickel (II) to 5'-nucleoside monophosphates and related compounds. 628 47

The Escherichia coli sulA gene product is a highly unstable protein, whose synthesis in response to DNA damage is associated with an inhibition of septation. Genetic evidence as well as sequence information suggests that the sulA gene is part of the E. coli SOS system and is induced after DNA damage. We have constructed a plasmid carrying only the sulA gene; this plasmid is stable only when it contains an amber mutation in the sulA structural gene. Using fragments of this plasmid, we have carried out in vitro transcription experiments and demonstrated one major start site for RNA transcription. We have mapped this initiation point to an adenylate residue 30 nucleotides before the protein start. Purified LexA protein completely abolishes this transcription, in agreement with the prediction made from the genetic and sequence information previously available.
J Mol Biol 1983 Dec 15
PMID:Transcription of the sulA gene and repression by LexA. 631 68

Aminoacyl-tRNA synthetases are capable of converting 5'-ATP into 5',5'-diadenosine tetraphosphate. The reaction reflects the reversal of enzyme-bound aminoacyl-adenylate by ATP instead of PPi. In the case of a few prokaryotic as well as eukaryotic aminoacyl-tRNA synthetases, the initial rate of diadenosine tetraphosphate synthesis can be greatly enhanced upon adding small amounts of zinc. This observation enables us to establish a relationship between diadenosine tetraphosphate, a nucleotide possibly involved in controlling cell proliferation, and a metallic cofactor, which is believed to play a role in tumour growth.
Mol Cell Biochem 1983
PMID:The role of zinc in 5',5'-diadenosine tetraphosphate production by aminoacyl-transfer RNA synthetases. 634 51

The three-dimensional structures of two animoacyl-tRNA synthetases, the methionyl-tRNA synthetase from Escherichia coli (MetRS) and the tyrosyl-tRNA synthetase from Bacillus stearothermophilus (TyrRS), show a remarkable similarity over a span of about 140 amino acids. The region of homologous folding corresponds to a five-stranded parallel beta-sheet, including a mononucleotide-binding fold. One cysteine and two histidine residues that were found to be invariant in the amino acid sequences occupy similar places in the nucleotide-binding fold. In TyrRS, these residues are close to the adenylate binding site, and in MetRS to the Mg2+-ATP binding site.
J Mol Biol 1983 Dec 25
PMID:Structural homology in the amino-terminal domains of two aminoacyl-tRNA synthetases. 636 12


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