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Biomedical subjects

A Banerjee

Publications and source records attributed to A Banerjee.

At least 469 records · Page 26Linked to original sources
PubMed1985

Interaction of reduced glutathione with bovine brain tubulin.

Incubation of phosphocellulose-purified tubulin with GSH at 30 degrees C results in an inhibition of colchicine binding activity. GSSG has a protective effect against the GSH-induced loss of colchicine-binding. Incubation of tubulin with GSH at 30 degrees C results in the formation of abnormal tubulin polymers which are insensitive to cold. Such aggregation is insensitive to antimicrotubular drugs. Aggregation is inhibited by GSSG but not by DTT or mercaptoethanol. GSH-induced aggregation is very sensitive to the ionic strength of the assembly medium; both the aggregation and colchicine binding inhibition induced by GSH are inhibited at higher ionic strength. These results indicate a very complex interaction of GSH with tubulin.

Animals↗
PubMed1985

Inhibition of soybean lipoxygenase 1 by N-alkylhydroxylamines.

Micromolar concentrations of N-octylhydroxylamine dramatically increase the induction period in the conversion of linoleic acid to 13(S)-hydroperoxy-cis-9,trans-11-octadecadienoic acid (13-HPOD) catalyzed by soybean lipoxygenase 1. The induction period produced by N-octylhydroxylamine is abolished by 13-HPOD but not by the corresponding hydroxy acid. Addition of a catalytic amount of lipoxygenase to a mixture of 13-HPOD and N-octylhydroxylamine results in consumption of approximately 1 mumol of 13-HPOD/mumol of N-octylhydroxylamine present. These results can be explained by a model in which 13-HPOD oxidizes the enzyme from an inactive ferrous form to an active ferric form, as proposed by previous workers, and N-octylhydroxylamine reduces the enzyme back to the ferrous form. Consistent with this model, the ESR signal at g = 6.1 characteristic of ferric lipoxygenase is rapidly abolished by N-octylhydroxylamine and can be regenerated by 13-HPOD. These results provide additional support for earlier proposals that ferric lipoxygenase is the catalytically active form and also establish a novel method of inhibiting enzymes in this class. The octyl group of N-octylhydroxylamine appears to contribute to binding near the iron, since hydroxylamine and N-methylhydroxylamine do not extend the induction period. In the n-RNHOH series, activity passes through an optimum at R = decyl.

Electron Spin Resonance Spectroscopy↗
PubMed1985

Conformations of bound nucleoside triphosphate effectors in aspartate transcarbamylase. Evidence for the London-Schmidt model by transferred nuclear Overhauser effects.

Transferred nuclear Overhauser effects were used to determine the conformations of ATP, CTP, and ITP bound to the regulatory site of aspartate transcarbamylase. The results are in accord with the predictions of the London-Schmidt model [London, R. E., & Schmidt, P. G. (1972) Biochemistry 11, 3136] and show that ATP and CTP bind in the anti conformation while ITP binds in the syn conformation.

Allosteric Site↗
PubMed1985

Asbestos-associated chromosomal changes in human mesothelial cells.

Replicative cultures of human pleural mesothelial cells were established from noncancerous adult donors. The cells exhibited normal mesothelial cell characteristics including keratin, hyaluronic acid mucin, and long branched microvilli, and they retained the normal human karyotype until senescence. The mesothelial cells were 10 and 100 times more sensitive to the cytotoxic effects of asbestos fibers than normal human bronchial epithelial or fibroblastic cells, respectively. In addition, cultures of mesothelial cells that survived two cytotoxic exposures of amosite fibers were aneuploid with consistent specific chromosomal losses indicative of clonal origin. These aneuploid cells exhibit both altered growth control properties and a population doubling potential of greater than 50 divisions beyond the culture life span (30 doublings) of the control cells.

Asbestos↗
PubMed1985

Molecular forms of GM2-activator protein. A study on its biosynthesis in human skin fibroblasts.

The biosynthesis and secretion of lysosomal GM2-activator was studied in fibroblasts from controls and patients of GM2 gangliosidosis metabolically labelled with [3H]-leucine. Immunoprecipitation was performed with affinity-purified antibodies to human kidney GM2-activator protein. Normal fibroblasts and fibroblasts of variant B and O of GM2 gangliosidosis secrete GM2-activator protein as a 24-kDa polypeptide, which is able to stimulate degradation of ganglioside GM2 by beta-hexosaminidase A in the in vitro assay. In the presence of 10mM NH4Cl the rate of secretion is twice as high as in normal fibroblasts. Intracellularly, GM2-activator protein is represented in these cell lines by polypeptides with apparent molecular masses ranging from 21 kDa-22.5 kDa. Under the same labelling conditions, in two cell lines of patients with variant AB of infantile GM2 gangliosidosis intracellularly only traces of GM2-activator were detectable, whereas significant amounts of polypeptides with molecular masses between 25 and 26.5 kDa could be precipitated from the media of these fibroblasts.

Cells, Cultured↗
PubMed1985

Serum protein polymorphisms in selected areas of West Bengal, India.

Serum proteins like haptoglobins and transferrin and total protein types were determined in healthy donors from West Bengal, with different levels of industrialisation and urbanisation, by disc gel electrophoresis. The frequency of the allele Hp2 was much higher in all the areas. A highly significant difference was observed between industrial and agricultural areas. However, the differences among the industrial districts were not significant except between the districts of Howrah and 24-Parganas.

Blood Proteins↗
PubMed1984

Three-dimensional structure of fungal proteinase K reveals similarity to bacterial subtilisin.

The three-dimensional structure of the fungal serine protease proteinase K has been determined at 3.3 A resolution by single crystal X-ray diffraction analysis. The enzyme crystallizes in the tetragonal space group P4(3)2(1)2 with cell constants a = b = 68.3 A, c = 108.5 A. The asymmetric unit consists of one monomer of 27 000 daltons mol. wt., approximately 50% higher than the so far assumed value of 18 500 daltons. The main chain fold of proteinase K shows a high degree of tertiary homology with the corresponding bacterial subtilisin BPN'. Proteinase K is the second enzyme in this family of serine proteases to be studied by X-ray diffraction, thus confirming the existence of two unrelated families of serine proteases in pro-and eukaryotes.

Bacteria↗
PubMed1984

Increased sister-chromatid exchange in bone-marrow cells of mice exposed to whole cigarette smoke.

Using defined cigarette smoke exposure conditions, BC3F1/Cum mice were exposed nose-only to two different types of whole cigarette smoke on a daily basis for 1 week and up to 46 weeks. The number of sister-chromatid exchanges (SCEs) per metaphase was determined in bone-marrow cells. Studies were scheduled so that all cytogenetic observations were made 2-3 days after the last smoke exposure. Exposure to either type of smoke on a daily basis for 1 week or up to 46 weeks resulted in a 2-fold increase in SCEs over sham-exposed control mice. In animals exposed either chronically or for 1 week to either type of smoke, the increase in SCEs persisted for at least 1 week after cessation of smoke exposure. This is the first demonstration of the induction of SCEs in laboratory animals that have been exposed to cigarette smoke in vivo.

Animals↗
PubMed1984

Protein synthesis in rabbit reticulocytes: a study of the mechanism of action of the protein factor RF that reverses protein synthesis inhibition in heme-deficient reticulocyte lysates.

A eukaryotic initiation factor 2 (eIF-2)-ancillary protein factor Co-eIF-2 promotes displacement of GDP from eIF-2 X GDP and facilitates ternary complex (Met-tRNAf X eIF-2 X GTP) formation in the presence of Mg2+. Heme-regulated protein synthesis inhibitor, HRI, phosphorylates the alpha-subunit of eIF-2 and thus inhibits ternary complex formation as Co-eIF-2 does not displace GDP from eIF-2 alpha (P) X GDP. RF, a high molecular weight cell supernatant factor, reverses protein synthesis inhibition in heme-deficient reticulocyte lysates and also reverses HRI inhibition of ternary complex formation. RF contains Co-eIF-2 activity. In addition, an active RF preparation contains excess alpha-subunit of eIF-2 in the free and unphosphorylated form and this alpha-subunit of eIF-2 is not phosphorylated by HRI and ATP. In this paper we report (i) an active RF preparation contains excess alpha-subunit of eIF-2 and this alpha-subunit can be phosphorylated by HRI and ATP in the presence of GDP; (ii) RF promotes ternary complex formation by eIF-2 X [3H]GDP with accompanying GDP displacement; (iii) in the presence of HRI and ATP, RF promotes ternary complex formation by eIF-2 X [3H]GDP without accompanying GDP displacement; (iv) in the presence of HRI and ATP, the ternary complex formed using RF is active in Met-tRNAf X 40S initiation complex formation; (v) both the ternary complex and the Met-tRNAf X 40S complex formation in the presence of HRI and ATP are completely inhibited by prior incubation of RF with GDP; (vi) upon further fractionation of an active RF fraction, a preparation can be obtained that contains HRI-sensitive Co-eIF-2 activity. However, this preparation does not efficiently reverse protein synthesis inhibition in heme-deficient reticulocyte lysates and does not contain excess alpha-subunit of eIF-2. Based on these observations, we have suggested (a) RF provides the unphosphorylated alpha-subunit to eIF-2 alpha (P) X GDP and restores eIF-2 activity. This RF activity is inhibited as the alpha-subunit in the RF preparation becomes phosphorylated by HRI and ATP in the presence of GDP; (b) RF contains Co-eIF-2 activity, which has dual functions: (i) stimulation of ternary complex formation by eIF-2 and (ii) GDP displacement from eIF-2 X GDP during ternary complex formation. In the presence of HRI and ATP, Co-eIF-2 but does not displace GDP from eIF-2 alpha(P) X GDP.

Adenosine Triphosphate↗
PubMed1984

Enzyme-linked immunosorbent assay for the ganglioside GM2-activator protein. Screening of normal human tissues and body fluids, of tissues of GM2 gangliosidosis, and for its subcellular localization.

An enzyme-linked immunosorbent assay was developed for the quantitation of the human activator protein for ganglioside GM2 degradation by beta-N-acetyl-D-hexosaminidase A. With this assay, various tissues and body fluids of normal subjects and of patients with variant forms of GM2 gangliosidosis were screened for their GM2-activator content. The highest content of this protein was found in kidney. Tissues from patients with variant AB of infantile GM2 gangliosidosis contained only low levels (up to 5% of that of normal controls) of cross-reacting material. On subcellular fractionation of normal human skin fibroblasts, the activator was found to co-distribute with the lysosomal marker enzyme beta-hexosaminidase.

Body Fluids↗