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At least 1,189 records · Page 66Linked to original sources
PubMed2004

Hypermethylation of 5'-region of the human calcitonin gene in leukemias: structural features and diagnostic significance.

Methylation of the 5'-region of the calcitonin gene was investigated in bone marrow and peripheral blood cells of 27 healthy volunteers and 25 leukemic patients. In all patients suffering from various forms of myeloid and lymphoid leukemia, hypermethylation of CpG sequences was observed in this region of the calcitonin gene. Cytosine hypermethylation in the CpG sequence did not involve cytosines of adjacent CpNpG sequences (where N is any nucleoside). The 5'-region of the calcitonin gene lacked CpNpG methylation both in healthy controls and in leukemic patients; this apparently represents specific "non-alternative" type of CpG methylation in the extended DNA sequence. Methylation of the calcitonin gene was monitored in 18 leukemic patients during malignant progression and medical treatment. Hypermethylation of the calcitonin gene was not observed on long-term clinical hematological remission. In ten patients characterized by unstable (or incomplete) remission hypermethylation of the calcitonin gene persisted through the whole period of observation. In relapses, hypermethylation of the calcitonin gene appeared again and in six patients, this "molecular relapse" being registered 1-8 months before onset of clinical and laboratory signs of disease progression. The leukemia-specific hypermethylation of CpG sequences of the 5'-region of the calcitonin gene is a promising prognostic and diagnostic marker of leukemias and might be useful for monitoring of this disease.

5' Flanking Region↗
PubMed1988

A simple structural feature is a major determinant of the identity of a transfer RNA.

Analysis of a series of mutants of an Escherichia coli alanine transfer RNA shows that substitution of a single G-U base pair in the acceptor helix eliminates aminoacylation with alanine in vivo and in vitro. Introduction of that base pair into the analogous position of a cysteine and a phenylalanine transfer RNA confers upon each the ability to be aminoacylated with alanine. Thus, as little as a single base pair can direct an amino acid to a specific transfer RNA.

Base Composition↗
PubMed1996

Expression and structural features of endoglin (CD105), a transforming growth factor beta1 and beta3 binding protein, in human melanoma.

Human endoglin (CD105) is a member of the transforming growth factor beta (TGF-beta) receptor family that binds TGF-beta1 and -beta3, but not TGF-beta2, on human endothelial cells. Immunohistochemical analyses demonstrated that CD105 is expressed on normal and neoplastic cells of the melanocytic lineage. The anti-CD105 MAb, MAEND3, stained 50, 25 and 34% of intradermal naevi, primary and metastatic melanomas investigated, respectively, and nine out of 12 melanoma cell lines. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that CD105 expressed by melanoma cells consists of a homodimeric protein with an apparent molecular weight of 180 and 95 kDa under non-reducing and reducing conditions. Cross-linking of 125I-labelled TGF-beta1 to melanoma cells, Mel 97, by disuccinimidyl suberate (DSS) demonstrated that CD105 expressed on pigmented cells binds TGF-beta1; the pattern of binding of TGF-beta1 to melanoma cells was found to be similar to that of human umbilical vein endothelial cells. The addition of exogenous, bioactive TGF-beta1 significantly (P<0.05) inhibited the growth of CD105-positive melanoma cells, Mel 97, but did not affect that of CD105-negative melanoma cells, F0-1. These data, altogether, demonstrate that CD105 is expressed on pigmented cells and might play a functionally relevant role in the biology of human melanoma cells by regulating their sensitivity to TGF-betas.

Animals↗
PubMed1997

Latent transforming growth factor-beta: structural features and mechanisms of activation.

Transforming growth factor-beta are cytokines with a wide range of biological effects. They play a pathologic role in inflammatory and fibrosing diseases such as nephrosclerosis. TGF-beta s are secreted in a latent form due to noncovalent association with latency associated peptide (LAP), which is a homodimer formed from the propeptide region of TGF-beta. LAP is disulfide linked to another protein, latent TGF-beta binding protein (LTBP). LTBP has features in common with extracellular matrix proteins, and targets latent TGF-beta to the matrix. Activation of latent TGF-beta can be accomplished in vitro by denaturing treatments, plasmin digestion, ionizing radiation and interaction with thrombospondin. The mechanisms by which latent TGF-beta is activated physiologically are not well understood. Results to date suggest an important role for proteases, particularly plasmin, although other mechanisms probably exist. A general model of activation is proposed in which latent TGF-beta is released from the extracellular matrix by proteases, localized to cell surfaces, and activated by cell-associated plasmin.

Animals↗
PubMed1968

A reappraisal of some structural features of bovine heart malate dehydrogenase.

1. Malate dehydrogenase of the mitochondrial type was prepared from an acetone-prepared powder of thoroughly washed minces of whole bovine heart by previously reported methods that were modified to give higher yields of the purified enzyme. 2. Determinations of the sedimentation and diffusion coefficients showed the molecular weight of the enzyme to be approx. 63000. The amino acid composition of the enzyme was also determined. Discrepancies between these data and similar data previously reported by Davies & Kun (1957) and Siegel & Englard (1962) were resolved. 3. ;Fingerprints' were made from tryptic digests of heat-denatured and of reduced and alkylated enzyme. These indicated that the enzyme is composed of a number of identical or similar sub-units.

Amino Acids↗
PubMed1970

Some structural features of the teichuronic acid of Bacillus licheniformis N.C.T.C. 6346 cell walls.

A teichuronic acid, containing glucuronic acid and N-acetylgalactosamine, was purified from acid extracts of Bacillus licheniformis 6346 cell walls as described by Janczura, Perkins & Rogers (1961). After reduction of the carboxyl function of glucuronic acid residues in the polysaccharide the reduced polymer contains equimolar amounts of N-acetylgalactosamine and glucose. Methylation of the reduced polysaccharide by the Hakamori (1964) technique showed the glucose residues to be substituted on C-4. A disaccharide, 3-O-glucuronosylgalactosamine, was isolated from partial acid hydrolysates of teichuronic acid. After N-acetylation the disaccharide produces chromogen readily on heating at pH7, in agreement with C-3 substitution of the reducing N-acetylamino sugar. Teichuronic acid also produces chromogen under the same conditions, with concurrent elimination of a modified polysaccharide from C-3 of reducing terminal N-acetylgalactosamine residues of the teichuronic acid chains. The number-average chain lengths of several preparations of teichuronic acid were estimated from the amounts of chromogen produced in comparison with the N-acetylated disaccharide. The values obtained are in good agreement with the weight-average molecular weight determined by ultracentrifugal analysis. The reducing terminals of teichuronic acid are shown to be exclusively N-acetylgalactosamine by reduction with sodium boro[(3)H]hydride. The number-average chain lengths of the teichuronic acid preparations were estimated by the extent of in corporation of tritium and are in agreement with values obtained by the other methods.

Bacillus↗
PubMed1978

Polypeptide linkages and resulting structural features as powerful chromogenic factors in the Lowry phenol reaction. Studies on a glycoprotein containing no Lowry phenol-reactive amino acids and on its desialylated and deglycosylated products.

With bovine serum albumin as the reference standard, the armadillo salivary-gland glycoprotein, although containing no chromogenic amino acids and only small amounts of colour-yielding peptides [Chou & Goldstein (1960) Biochem. J. 75, 100-115], is highly reactive in the Lowry phenol protein assay [Wu & Pigman (1977) Biochem. J. 161, 37-47]. After desialylation and Smith degradation of the glycoprotein, the Lowry phenol value increased by 13 and 30% respectively, which suggests that both sialic acid and N-acetylhexosamine exert shielding effects in this reaction. Acid hydrolysis for 30 min decreased the Lowry phenol value by more than 45%, which indicates that the peptide linkages and steric features affect the Lowry phenol reactivity. After hydrolysis for up to 6h, the remaining Lowry phenol value of the partially hydrolysed core protein paralleled the amount of unhydrolysed peptides, inferring that both acid-sensitive and acid-resistant chromophoric peptides are fairly evenly distributed along the whole polypeptide chain. As with bovine serum albumin, more than 80% of the colour yield obtained in the Lowry phenol assay with this glycoprotein is Cu2+-dependent.

Animals↗
PubMed1981

Determination of some biochemical and structural features of alcohol dehydrogenases from Drosophila simulans and Drosophila virilis. Comparison of their properties with the Drosophila melanogaster Adhs enzyme.

The biochemical properties of the enzyme alcohol dehydrogenase of two different Drosophila species, Drosophila simulans and Drosophila virilis, were studied and compared with those of Drosophila melanogaster Adhs enzyme. All of them consist of two identical subunits of molecular weight 27800 and share significant similarities in function. The substrate specificities of these enzymes were characterized and Km(app.) and Vmax.(app.) values were calculated. All these alcohol dehydrogenases show greater affinity for secondary rather than for primary alcohols. The amino acid compositions of the three enzymes were determined, and there is a close similarity between the D. simulans and the D. melanogaster enzymes, but there are significant differences from the alcohol dehydrogenase of D. virilis. The N-terminal amino acid is blocked and the C-terminal amino acid is the same for all three alcohol dehydrogenases. The enzymes from the three species were carboxymethylated and digested with trypsin. The peptide 'maps' reveal, as expected, more homologies between the enzymes of D. simulans and D. melanogaster than with the enzyme of D. virilis.

Alcohol Oxidoreductases↗