Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An unusual class of wheat germ tRNAs has been isolated which completely lacks ribothymidine (rT) and contains an unmodified uridine in its place. We discuss here the isolation, identification and properties of these tRNAs. The rT-lacking tRNAs of wheat germ are essentially limited to the glycine isoacceptors (a minimum of five identifiable species), three threonine and at least, one tyrosine tRNA. All tRNAs were obtained 70-100% pure by chromatographic methods, and were detected by their ability to be methylated by E. coli rT-forming uracil methyltransferase with methyl-labeled S-adenosyl-L-methionine (SAM) as the methyl donor. In vitro methylation of each of the tRNAs resulted in the formation of 1 mole of rT per mole of tRNA. In the one case analyzed in detail (tRNA1Gly), all of the rT was found to be located at the 23rd position from the 3' end of the tRNA molecule. Following complete digestion of four highly purified glycine isoacceptors (tRNAGly1,4,5,6) to nucleosides and subsequent periodate oxidation and 3H potassium borohydride reduction, all were found to contain an unusually high level of 5-methylcytidine (m5C) (3-4 residues per molecule), and all contained no rT. The possible correlation between the presence of m5C and the absence of rT is discussed. All of the chromatographically purified glycine tRNAs function in a wheat germ cell-free protein synthesizing system and polymerize glycine in response to either poly G or poly (G, U).
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PMID:Wheat germ tRNAs containing uridine in place of ribothymidine: a characterization of an unusual class of eukaryotic tRNAs. 65 15

A 7-methylguanine (m7G) specific tRNA methyltransferase from E. coli MRE 600 was purified about 1000 fold by affinity chromatography on Sepharose bound with normal E. coli tRNA. The purified enzyme catalyzes exclusively the formation of m7G in submethylated bulk tRNA of E. coli K12 met- rel-. The purified enzyme transfers the methyl group from S-adenosyl-methionine to initiator tRNA of B. subtilis and 0.8 moles m7G residues are formed per mole tRNA. It is suggested that the enzyme specifically recognizes the extra arm unpaired guanylate residue.
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PMID:7-Methylguanine specific tRNA-methyltransferase from Escherichia coli. 79 33

The addition of solutions of bovine myelin basic protein to suspensions of unilamellar vesicles prepared from whole myelin suspensions results in the rapid equilibrium association of the vesicles into dimers, followed by time-dependent aggregation reactions. Other cationic proteins also induce the dimerization of the vesicles and equilibrium constants for dimer formation are obtained for bovine myelin basic protein, lysozyme, polyhistidine and myelin basic protein from carp, which differs from the bovine protein in that it contains no methylarginine residues. The bovine protein is more efficient at inducing dimer formation than the carp protein by approximately 0.93 kcal/mole; the carp protein is approximately as effective as the other cationic proteins examined. Complete methylation of the bovine MBP by AdoMet:MBP methyltransferase increases the interaction between MBP and the membrane by approximately 0.13 kcal/mole, consistent with the suggestion that a large portion of the free energy difference between the carp and bovine proteins arises from favorable interactions involving the methylarginine residues.
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PMID:Mechanism of the interaction between myelin basic protein and the myelin membrane; the role of arginine methylation. 244 Apr 26

The specificity of phosphatidylethanolamine (PE) N-methyltransferase for molecular species of PE has been investigated. Phosphatidylcholine (PC), synthesized by incubation of [methyl-3H]S-adenosyl-L-methionine with microsomes or pure enzyme (Ridgway, N. D., and Vance, D. E. (1987) J. Biol. Chem. 262, 17231-17239) plus microsomal PE, had a distribution of methyl label in molecular species similar to the mole percent distribution of molecular species in the precursor PE. A similar lack of specificity was observed with PE that was synthesized from egg PC by transphosphatidylation with phospholipase D. Phosphatidyl-N-monomethylethanolamine (PMME) and phosphatidyl-N,N-dimethylethanolamine (PDME), both with the acyl composition of egg PC, were methylated by the pure enzyme and showed a distribution of labeled molecular species in PDME and PC, respectively, similar to the mole percent distribution of egg PC. Results with synthetic PEs and pure methyltransferase showed higher rates of methylation with more unsaturated species. Long chain saturated PEs (e.g. dipalmitoyl-PE) were not methylated by the enzyme. Maximal methylation rates were obtained with two or more double bonds in the substrate PE. Rates of methylation of the saturated and monoenoic PEs could be enhanced when 40 mol % polyunsaturated-rich microsomal PC was included in the mixed micelles. PC isolated from primary cultures of rat hepatocytes pulsed with [methyl-3H]methionine was analyzed by high performance liquid chromatography. Initially, the labeling pattern of PC molecular species varied slightly from that of total hepatocyte PE and hepatocyte microsomal PE. 1-Palmitoyl-2-docosahexaenoyl-PC had the highest specific activity at the end of the pulse and was preferentially labeled relative to the mole percent distribution of hepatocyte PE molecular species. During the 24-h chase period both the percent distribution of label and specific activity of this species of PC declined. In the same time period, there was a corresponding increase in specific activity and percent distribution of label in 1-palmitoyl and 1-stearoyl species with linoleate and arachidonate in the sn-2 position.
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PMID:Specificity of rat hepatic phosphatidylethanolamine N-methyltransferase for molecular species of diacyl phosphatidylethanolamine. 318 18

Extracts of Methanosarcina barkeri possess a specific methyltransferase that catalyzes the transfer of the methyl group of methanol to 2-mercaptoethanesulfonic acid. Over a fourfold range in added 2-mercaptoethanesulfonic acid, the formation of 2-(methylthio)ethanesulfonic acid exhibited a 1:1 ratio to 2-mercaptoethanesulfonic acid added. This reaction required adenosine 5'-triphosphate; a maximal ratio (mole/mole) of 85 methyl groups was transferred per adenosine 5'-triphosphate added. The methyltransferase was found in extracts of methanol-grown cells as well as in extracts of hydrogen-grown cells. In extracts of cells grown on either substrate, 2-(methylthio)ethanesulfonic acid was formed from added methanol or methylamine but not from acetate.
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PMID:Methyl-coenzyme M, an intermediate in methanogenic dissimilation of C1 compounds by Methanosarcina barkeri. 644 45

Experiments were carried out to investigate the time course of the release of catecholamine, dopamine-beta-hydroxylase (DBH) and adenine nucleotides from isolated chromaffin cells of guinea-pig adrenal gland. When the isolated chromaffin cells were incubated with medium containing acetylcholine (ACh) (0.1 mM), veratridine (0.1 mM) or scorpion (Leiurus quinquestriatus) venom, (10 micrograms/ml.), catecholamine was released into the medium. Catecholamine secretion induced by veratridine or scorpion venom was inhibited by tetrodotoxin (1 microM) but not by atropine (0.1 mM) plus hexamethonium (0.1 mM). On the other hand, the secretory response to ACh was abolished by the cholinergic blocking drugs but not by tetrodotoxin. DBH was released together with catecholamine into the medium in which cells were suspended with these drugs. The ratio of catecholamine (n-mole) to DBH activity (n-mole/hr) appearing in the supernatant was 7.08 +/- 0.55, 6.60 +/- 0.27 and 8.91 +/- 0.47 for ACh, veratridine and scorpion venom, respectively. These values were close to that found in the lysate of chromaffin granules obtained from guinea-pig adrenal glands (7.37 +/- 0.39). The application of ACh or veratridine to perifused chromaffin cells was found to cause a parallel increase in catecholamine and DBH secretion in the perifusion medium without corresponding amounts of phenylethanolamine-N-methyltransferase leakage. However, DBH secretion tended to last for a longer period than catecholamine secretion. Adenine nucleotides were released from perifused chromaffin cells together with catecholamine, by ACh and veratridine. ATP added to the perifusion medium was metabolized to ADP and AMP, of which the ratio (ATP, 21.6%; ADP, 34%; AMP, 17.9%) was close to those of adenine nucleotides released from the cells. The secretion of adenine nucleotides induced by both secretagogues ceased much faster than the catecholamine secretion, so that molar ratio of catecholamine to adenine nucleotides was gradually increased during and after stimulation. The results indicate that catecholamine secretion is accompanied with a simultaneous release of DBH and ATP from adrenal chromaffin cells. Therefore, it is suggested that the delayed output of DBH, unlike catecholamine secretion, in perfused adrenal glands results from the presence of a diffusion barrier for this protein. The releasable secretory granules of isolated chromaffin cells are suggested to be heterogeneous with respect to the ratio of catecholamine to ATP.
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PMID:Time course of release of catecholamine and other granular contents from perifused adrenal chromaffin cells of guinea-pig. 662 Jan 78

Phenylethanolamine-N-methyltransferase (PNMT) catalyzes the conversion of norepinephrine to epinephrine. The enzyme, obtained from bovine adrenal gland, was incubated with PbCl2 at 23 degrees for various times prior to assay at 37 degrees. Inhibition developed slowly and reached a maximum after 45 min. In the presence of 4.5 nmoles PbCl2 (15 microM), 5.8 microgram protein was inhibited 50%, and inhibition was complete at 18 nmoles PbCl2 (60 microM). At maximum inhibition the PbCl2: protein ratio was 3.1 nmoles PbCl2/microgram protein. In the presence of PbCl2, the graph of enzyme activity versus protein concentration intercepted the abscissa to the right of the origin, indicating that lead is an irreversible or very slowly reversible inhibitor. The activity of PNMT which had been exposed to PbCl2 (2.6 or 5.2 nmoles PbCl2/microgram protein) was not restored by the addition of EDTA, DL-penicillamine or 1,3-dithiothreitol even when the concentration of the chelator was in 10 to 200-fold mole excess over PbCl2. DL-Penicillamine and 1,3-dithiothreitol were unable to prevent PbCl2 inhibition of the enzyme when combined with PbCl2 1 hr before addition of enzyme. EDTA could prevent 40% of PbCl2 inhibition but a decrease in total enzyme activity was noted in the presence of this chelator. Dialysis of the PbCl2-inhibited enzyme against buffer alone or buffer plus DL-penicillamine did not result in restoration of PNMT activity.
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PMID:Inhibition by lead of phenylethanolamine-N-methyltransferase. 711 20

Hydroxyindole-O-methyltransferase (HIOMT) activity for the synthesis of melatonin and 5-methoxytryptophol, both 5-methoxyindoles, was measured in the pineal, the Harderian gland and the retina of the mole rat and in the pineal of the mouse "eyeless". In the pineal and the Harderian gland of the mole rat a larger amount of 5-methoxytryptophol than of the melatonin is synthesized. 5-Methoxyindole synthesis is extremely high in the Harderian gland, whereas in the retina HIOMT activity is low and variable. In the pineal of the mouse "eyeless", a low 5-methoxyindole synthesis showing no circadian rhythm is demonstrated. It is concluded that, besides the generally accepted regulation of the indole metabolism by light, in species with atrophied eyes having Harderian glands (mole rat) and in species without eyes other factors than light might be responsible for the indole metabolism in the pineal gland.
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PMID:Preliminary investigations of melatonin and 5-methoxy-tryptophol synthesis in the pineal, retina, and harderian gland of the mole rat and in the pineal of the mouse "eyeless". 746 37

Lactobacillus leichmannii thymidylate synthase (5,10-CH2-H4PteGlu:dUMP C-methyltransferase, EC 2.1.1.45) forms a tight and stable covalently bonded ternary complex with the inhibitor 5-FdUMP in the presence of the cofactor 5,10-CH2-H4-PteGlu. 'Filter assay' employing the radioactive nucleotide ligand showed that 2 moles of FdUMP are bound per mole enzyme during the ternary complex formation with the L. leichmannii dTMP synthase. This is in line with our earlier observation on the Streptococcus faecium thymidylate synthase [Narasimha Rao, K & Kisliuk R L (1983), Proc Natl Acad Sci USA, 80, 916-920]. The enzyme has Km values of 6.3 x 10(-6) M, 8.2 x 10(-5) M and 1.0 x 10(-4) M for dUMP, (dl)-L-H4PteGlu and Mg2+ respectively; Vmax for dUMP, (dl)-L-H4PteGlu and Mg2+ are; 0.55, 0.5 and 1.1 respectively. It has K(i) values of 6.7 x 10(-6) M, 2.2 x 10(-6) M, 5.0 x 10(-5) M and 2.0 x 10(-4) M for FdUMP, dTMP, MTX and Ca2+ respectively. The type of enzyme inhibition with FdUMP, dTMP, MTX and Ca2+ was competitive. dTMP Studies clearly show the 'end product' inhibition of the enzyme.
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PMID:Ternary complex formation with 5-fluoro-2'-deoxyuridylate and the kinetic properties of thymidylate synthase from Lactobacillus leichmannii. 835 17

In prion-related encephalopathies, the cellular prion protein (PrP(C)) undergoes a change in conformation to become the scrapie prion protein (PrP(Sc)) which forms infectious deposits in the brain. Conceivably, the conformational transition of PrP(C) to PrP(Sc) might be linked with posttranslational alterations in the covalent structure of a fraction of the PrP molecules. We tested a synthetic peptide corresponding to residues 106-126 of human PrP for the occurrence of spontaneous chemical modifications. The only asparagine residue, Asn108, was deamidated to aspartic acid and isoaspartic acid with a half-life of about 12 days. The same posttranslational modifications were found in recombinant murine full-length protein. On aging, 0.8 mol of isoaspartyl residue per mole of protein was detected by the protein-l-isoaspartyl methyltransferase assay (t(1/2) approximately 30 days). Mass spectrometry and Edman degradation of Lys-C fragments identified Asn108 in the amino-terminal flexible part of the protein to be partially converted to aspartic acid and isoaspartic acid. A second modification was the partial isomerization of Asp226' which is only present in rodents.
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PMID:Spontaneous deamidation and isomerization of Asn108 in prion peptide 106-126 and in full-length prion protein. 1044 69


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