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)

Arginyl-tRNA synthetase from Escherichia coli K12 has been purified more than 1000-fold with a recovery of 17%. The enzyme consists of a single polypeptide chain of about 60 000 molecular weight and has only one cysteine residue which is essential for enzymatic activity. Transfer ribonucleic acid completely protects the enzyme against inactivation by p-hydroxymercuriben zoate. The enzyme catalyzes the esterification of 5000 nmol of arginine to transfer ribonucleic acid in 1 min/mg of protein at 37 degrees C and pH 7.4. One mole of ATP is consumed for each mole of arginyl-tRNA formed. The sequence of substrate binding has been investigated by using initial velocity experiments and dead-end and product inhibition studies. The kinetic patterns are consistent with a random addition of substrates with all steps in rapid equilibrium except for the interconversion of the cental quaternary complexes. The dissociation constants of the different enzyme-substrate complexes and of the complexes with the dead-end inhibitors homoarginine and 8-azido-ATP have been calculated on this basis. Binding of ATP to the enzyme is influenced by tRNA and vice versa.
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PMID:Arginyl-tRNA synthetase from Escherichia coli K12. Purification, properties, and sequence of substrate addition. 3 99

Minimum satisfactory concentrations of thymine and thymidine were determined for the growth of a high thymine-requirng (thy) mutant to Escherichia coli strain J5-3. Cultures were then grown in the presence of these concentrations of non-radioactive ('cold') pyrimidine together with 5 microCi/ml [methyl-3H)thymine, or [methyl-3H)thymidine (specific activities 5 Ci/m mole), and the uptake of radioactivity into ice cold trichloroacetic acid insoluble material determined. By far the most efficient labelling system was obtained if the label was supplied as radioactive thymidine and growth requirements satisfied by thymine alone. The addition of deoxyadenosine to the labelled thymidine/unlabelled thymine system dramatically reduced uptake of label. The addition of radioactive thymine with either thymine or thymidine to ensure satisfactory growth gave poor labelling. Using the [methyl-3H] thymidine/thymine system it was possible to increase the concentration of thymine from 8 to 64 microgram/ml with only a 25% reduction in label uptake after a 2 h period. The same system was also shown to be most efficient for labelling a thy derivative of another K12 strain, a thymine low-requiring (tir) K12 strain, a thy mutant of Klebsiella aerogenes 418 and a tir derivative of Salmonella typhimurium LT2.
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PMID:Preferential uptake of thymidine by thymineless enterobacteria: its significance in DNA labelling. 35 30

The structure of the lipopolysaccharide from Escherichia coli K12, strain CR34 has been investigated. The lipopolysaccharide contains D-galactose, D-glucose, D-glucosamine, L-glycero D-mannoheptose, 2-keto-3-deoxyoctonate and lipid A. The core region does not contain D-glucosamine but contains galactose, glucose, and heptose in the molar ratios 1:3:6. Methylations were performed on the lipopolysaccharide and on the degraded polysaccharide obtained after acetic acid hydrolysis of the lipopolysaccharide. It was found that galactose is in terminal position partly in the form of galactopyranose, partly in the form of galactofuranose. A part of the heptose was found as unsubstituted heptofuranose. A mole of glucose was 1 leads to 2 linked and another mole of glucose was 1 leads to 6 linked. Periodate oxidation of the lipopolysaccharide followed by borohydride reduction eliminates galactose and only a part of glucose and of heptose. A mole of heptose gave mannose and thus it is unsubstituted in C6 and C7. One mole of glucose and one mole of heptose were not degraded by periodate oxidation.
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PMID:[Study of the lipopolysaccharide from Escherichia coli K12 CR34]. 77 Jan 68

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

We have used polymerase chain reaction (PCR), an amplification procedure, and oligonucleotide hybridization to detect ras gene point mutations in DNA from melanoma tumor samples. Genomic DNA was examined from 40 specimens of melanotic lesions, including benign nevi, primary melanomas, lymph node metastases, and systemic metastases. Adjacent normal skin or peripheral blood was analyzed as control material in 28 cases. ras mutations were detected overall in 25% of malignant tumors. In addition, mutations of all three ras genes were detected. We observed ras mutations in 2 of 4 benign atypical nevi (2 X K12), 4 of 22 primary melanomas (3 X K12, 1 X H12, 1 X N61), and 4 of 14 secondary (5 X K12, 1 X N61) tumors. One with a primary melanoma had concurrent K12 and H12, and two patients with secondary tumors had concurrent K12/N61 and K12 Asp/K12 Val mutations, respectively, making a total of 10 of 40 (25%) patients with ras mutations. This is the first demonstration of K-ras mutations in human melanoma. The presence of K-ras mutations in nevi, putative melanoma precursors, suggests that ras activation may be an early event in melanoma development. No correlation between tumor thickness and the presence of a ras mutation was observed.
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PMID:ras mutations in human melanotic lesions: K-ras activation is a frequent and early event in melanoma development. 269 57

1. Intracellular K increases the ouabain-sensitive Na-K exchange in human red blood cells. Pump rate increases hyperbolically with internal K with a K12 for K of 2.58 m-mole/l. red blood cells. Li also stimulates the pump rate, but with a much higher K12. The stimulation does not result from a change in the affinity of the pump for its substrates Na, K or Mg or for the product, phosphate. 2. The effect of cell K on the Na-Na exchange is biphasic. At low concentrations it decreases the exchange rate but then the exchange increases linearly with cell k concentration. 3. Stimulation of the pump rate by internal K can be demonstrated in reconstituted ghosts but only if the ratio of the volume of cells to that of solution at the time of haemolysis is high. Stimulation is not observed if the ghosts contain an efficient system for rephosphorylating ADP to ATP, such as creatine phosphate and creatine kinase, or if the measurements are made with iodoacetamide which inhibits rephosphorylation of ADP by inhibiting the enzyme glyceraldehyde-3-phosphate dehydrogenase. 4. Cells with low internal K and Li have low ATP concentrations, and ATP increases hyperbolically with internal K or Li with the same K12 as does the pump rate. In cells depleted of substrate intracellular K does not stimulate the pump rate. 5. The effect of K and Li on the pump rate probably does not result from enhanced activity of any of the enzymes below phosphofructokinase in the glycolytic pathway.
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PMID:Internal potassium stimulates the sodium-potassium pump by increasing cell ATP concentration. 732 Sep 24

Complex formation in aqueous solutions of trans-cinnamic acid or trans-cinnamate ion (the substrate, S) and alpha-cyclodextrin (the ligand, L) can be described quantiatively as the 1:1 and 1:2 complexes, SL and SL2. The solubility, spectral, and potentiometric data over a wide range of ligand concentrations yielded consistent estimates of the complex association constants. For cinnamic acid at 25 degrees K11 = 2260 M-1, delta H degree 11 = 9.3 kcal/mole, and delta S degree 11 = -8 e.u.; and K12 = 60 M-1, delta H degree 12 = -12 kcal/mole, and delta S degree 12 = -26 e.u. For cinnamate ion at 25 degrees, K11 = 110 M-1, delta H degree 11 = -1.9 kcal/mole, and delta S degree 11 = +11 e.u.; and K12 = 15 M-1, delta H degree 12 = 9 kcal/mole, and delta S degree 12 = -15 e.u. (all entrophy changes are unitary quantities). Thermodynamic cycles for the complexes, using solubility data, reveal that complex formation in the solid phase is thermodynamically spontaneous but that complex stability is greater in ageous solution than in the solid phase.
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PMID:trans-Cinnamic acid--alpha-cyclodextrin system as studied by solubility, spectral, and potentiometric techniques. 735 18

Keratins are the type I and II intermediate filament proteins which form a cytoskeletal network within all epithelial cells. They are expressed in pairs in a tissue- and differentiation-specific fashion. Epidermolysis bullosa simplex (EBS) was the first human disorder to be associated with keratin mutations. The abnormal keratin filament aggregates observed in basal cell keratinocytes of some EBS patients are composed of keratins K5 and K14. Dominant mutations in the genes encoding these proteins were shown to disrupt the keratin filament cytoskeleton resulting in cells that are less resilient and blister with mild physical trauma. Identification of mutations in other keratin genes soon followed with attention focussed on disorders showing abnormal clumping of keratin filaments in specific cells. For example, in bullous congenital ichthyosiform erythroderma, clumping of filaments in the suprabasal cells led to the identification of mutations in the suprabasal keratins, K1 and K10. Mutations have now been identified in 18 keratins, all of which produce a fragile cell phenotype. These include ichthyosis bullosa of Siemens (K2e), epidermolytic palmoplantar keratoderma (K1, K9), pachyonychia congenita (K6a, K6b, K16, K17), white sponge nevus (K4, K13), Meesmann's corneal dystrophy (K3, K12), cryptogenic cirrhosis (K8, K18) and monilethrix (hHb6, hHb1).In general, these disorders are inherited as autosomal dominant traits and the mutations act in a dominant-negative manner. Therefore, treatment in the form of gene therapy is difficult, as the mutant gene needs to be inactivated. Ways of achieving this are actively being studied. Reliable mutation detection methods from genomic DNA are now available. This enables rapid screening of patients for keratin mutations. For some of the more severe phenotypes, prenatal diagnosis may be requested and this can now be performed from chorionic villus samples at an early stage of the pregnancy. This review article describes the discovery of, to date, mutations in 18 keratin genes associated with inherited human diseases.
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PMID:The molecular genetics of keratin disorders. 1268 39