Browsing by Author "D.P. Burma"

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5S RNA may not have highly ordered structure like 4S RNAS
(1982) D.S. Tewari; D.P. Burma
The rates of hydrolysis of the following polyribonucleotides as catalysed by RNase I, an enzyme specific for single stranded RNAs, follow the sequence shown; poly (A) > 23S RNA > 5S RNA ≫ 16S RNA > 4S RNA = poly (I). poly (C). The rates were measured by direct spectrophotometric as well as by trichloroacetic acid precipitation methods. The extents of inhibition of RNase I-catalysed hydrolysis of poly (A) by each of the above-mentioned polyribonucleotides follow the reverse order. Taking into account the fact that double stranded RNAs are inhibitory to RNase I it may be concluded from the above results that 5S RNA has much less ordered structure than 4S RNAs. This prediction is contrary to expectations and its validity will be known when the tertiary structure of 5S RNA will be worked out. These results also indicate that 16S RNA may have more folded structure than 23S RNA. © 1982.
A biosynthetic method for preparing 35S-labelled lipoic acid
(1965) S.K. Mitra; R.K. Mandal; D.P. Burma
[No abstract available]
Alteration of the structure of the Escherichia coli ribosomes on treatment with Fab fragment of immunoglobulin raised against the ribosomes
(Springer India, 1979) M. Das; D.P. Burma
Rabbits were immunised against Escherichia coli ribosomes and the partially purified immunoglobulin G fraction had maximum ability to precipitate the ribosomes as well as the extracted ribosomal proteins. By digestion of immuno-globulin G with papain, monovalent Fab fragments were produced. The 70 S ribosome and its subunits (50 S and 30 S) were separately treated with Fab and then tested in the kinetic assay of degradation of ribosomes by ribonuclease I at various Mg2+ concentrations. Treated ribosomes and their subunits were degraded at faster rates than the nontreated ones; the rates in both the control and the treated cases were dependent on the concentration of Mg2+. These results indicate the unfolding of the structure of the ribosome on treatment with antibody fragments, which may be due to the weakening of the interaction between rRNAs and ribosomal proteins. © 1979 Indian Academy of Sciences.
Conformational change of 50 S ribosomes on enzymatic binding of phenylalanyl-tRNA
(1985) S. Srivastava; D.P. Burma
Tight couple 70 S ribosmes are converted to loose couple ones on enzymatic binding of phenylalanyl-tRNA. Enzymatic binding at 0°C as well as nonenzymatic binding does not lead to any change. Further, no change takes place when the P site is occupied by N-acetylphenylalanyl-tRNA. Loose couple 70 S ribosomes are not affected by either enzymatic or nonenzymatic binding of phenylalany-tRNA. © 1985.
CROSSLINKING OF 16S AND 23S RNAs PRESENT IN THE COMPLEX FORMED UNDER RECONSTITUTION CONDITION
(Indian Academy of Sciences, 1982) B. Nag; D.P. Burma
[No abstract available]
Differences in physical and biological properties of 50S ribosomes and 23S RNAs derived from tight and loose couple 70S ribosomes
(1984) D.P. Burma; A.K. Srivastava; S. Srivastava; D.S. Tewari; D. Dash; S.K. Sengupta
Tight couple (TC) 50S ribosomes on treatment with kethoxal lose their capacity to associate with 30S ribosomes whereas loose couple (LC) 50S ribosomes on such treatment fully retain their association capacity. The same is true for 23S RNAs isolated from treated 50S ribosomes or isolated 23S RNAs directly treated with kethoxal, so far as their capacity to associate with 16S RNA is concerned. At certain Mg++ concentrations TC 23S RNA is highly susceptible to the nucleolytic action of single-strand specific enzyme RNase I; LC 23S RNA is quite resistant. The Mg++-dependencies of the two species of 23S RNAs for association with 16S RNA are also quite different. The fluorescence enhancement of ethidium bromide due to binding to TC 23S RNA is slightly less than LC 23S RNA. The hyperchromicity of LC 23S RNA due to thermal denaturation is somewhat more than TC 23S RNA. LC 23S RNA has slightly more elliptic CD spectrum than TC 23S RNA. These results clearly show that 23S RNAs present in TC and LC 50S ribosomes are distinct from each other. It has been recently demonstrated in this laboratory that they can be interconverted by the agents involved in translocation and thus appear to be conformomers. © 1984.
Digoxin toxicity and electrolytes: A correlative study
(1983) S. Sundar; D.P. Burma; S.K. Vaish
Serum levels of sodium, potassium, calcium, magnesium and digoxin were studied in 67 patients on maintenance dose of digoxin, 42 with digitoxicity and 25 without. The mean serum digoxin level of toxic group was significantly higher (p < 0.001) than non-toxic group. The mean serum potassium was significantly lower in toxic group (p < 0.05) as compared to the non-toxic group. Of the toxic patients, 23.8% had hypokalemia. Hypokalemia resulted by significantly higher (p < 0.005) dose of diuretic use in toxic group. The mean serum digoxin level of hypokalemic toxic group was significantly lower as compared to the normokalemic toxic group (p < 0.001) and it was interesting to note that all hypokalemic toxic patients had their serum digoxin levels below 3 ng/ml (3.84 n mol/ml) and well within therapeutic range. There was a positive correlation between serum digoxin and potassium level amongst toxic patients (p < 0.001). Thus, in patients on maintenance dose of digoxin therapy, use of large dosage of diuretics may result in hypokalemia, causing digitalis toxicity even at low serum digoxin levels. Serum digoxin level alone may fail as an independent guide in diagnosis of digoxin toxicity in presence of hypokalemia.
DNA-dependent incorporation of guanylate residues into polynucleotide material
(1965) C. Majumdar; D.P. Burma
[No abstract available]
Do ribosomal RNAs act merely as scaffold for ribosomal proteins?
(Springer India, 1985) D.P. Burma; A.K. Srivastava; S. Srivastava; D. Dash; D.S. Tewari; B. Nag
Investigations that are being carried out in various laboratories including ours clearly provide the answer which is in the negative. Only the direct evidences obtained in this laboratory will be presented and discussed. It has been unequivocally shown that the interaction between 16S and 23S RNAs plays the primary role in the association of ribosomal subunits. Further, 23S RNA is responsible for the Binding of 5S RNA to 16S.23S RNA complex with the help of three ribosomal proteins, L5, L18, L15/L25. The 16S.23S RNA complex is also capable of carrying out the following ribosomal functions, although to small but significant extents, with the help of a very limited number of ribosomal proteins and the factors involved in protein synthesis: (a) poly U-Binding, (B) poly U-dependent Binding of phenylalanyl tRNA, (c) EF-G-dependent GTPase activity, (d) initiation complex formation, (e) peptidyl transferase activity (puromycin reaction) and (f) polyphenylalanine synthesis. These results clearly indicate the direct involvement of rRNAs in the various steps of protein synthesis. Very recently it has Been demonstrated that the conformational change of 23S RNA is responsible for the translocation of peptidyl tRNA from the aminoacyl (A) site to the peptidyl (P) site. A model has Been proposed for translocation on the Basis of direct experimental evidences. The new concept that ribosomal RNAs are the functional components in ribosomes and proteins act as control switches may eventually turn out to Be noncontroversial. © 1985 Printed in India.
Effect of denatured DNA's on Salmonella typhimurium ribonuclease I
(1969) A.K. Mukhopadhyay; D.P. Burma
[No abstract available]
Effects of ethidium bromide and berenil on protein synthesis
(Springer India, 1979) Ziledar Ali; D.P. Burma
The effects of ethidium bromide, an intercalating dye and berenil, a nonintercalating dye on the biological activities of Escherichia coli ribosomes have been studied. Ethidium bromide treatment drastically reduced both enzymatic and nonenzymatic initiation complex formation, enzymatic as well as nonenzymatic binding of phenylalanyl tRNA, peptidyl transferase, GTPase as well as the overall protein synthesising activity as measured by the poly U-dependent polymerization of phenylalanine. On berenil treatment, however, only enzymatic formation of the initiation complex is marginally reduced. Other reactions are not markedly affected except the enzymatic phenylalanyl tRNA binding which is slightly decreased only at high Mg2+ concentration; the treated ribosome has lowered polymerizing activity at sub-optimal Mg2+ concentration (10 mM). Although it has already been shown in this laboratory that treatment with either dye leads to the unfolding of the structure of the ribosome, the present studies indicate that berenil treatment does not alter the structure of the ribosome drastically in contrast to ethidium bromide treatment. © 1979 Indian Academy of Sciences.
Effects of polycationic amines and streptomycin on the structure of N ethylmaleimide treated rat liver ribosome
(1976) S. Ghosh; D.P. Burma
[No abstract available]
Effects of spermidine, spermine and N ethylmaleimide on the structure of the rat liver ribosome
(1976) S. Ghosh; D.P. Burma
[No abstract available]
Enzymatic activity of ribosomal RNA
(1993) D.P. Burma
[No abstract available]
How and why ribosome?
(1995) D.P. Burma
[No abstract available]
Immunoprecipitation of 70S, 50S and 30S ribosomes of Escherichia coli
(Springer India, 1980) D.K. Lahiri; D.P. Burma
Antibodies were raised in rabbits against 70S ribosomes, 50S and 30S ribosomal subunits individually. Purified immunoglobulins from the antiserum against each of the above ribosomal entities were tested for their capabilities of precipitating 70S, 50S and 30S ribosomes. The observations revealed the following: (i) The antiserum (IgG) raised against 70S ribosomes precipitates 70S ribosomes completely, while partial precipitation is seen with the subunits, the extent of precipitation being more with the 50S subunits than with 30S subunits; addition of 50S subunits to the 30S subunits facilitates the precipitation of 30S subunits by the antibody against 70S ribosomes. (ii) Antiserum against 50S subunits has the ability to immunoprecipitate both 50S and 70S ribosomes to an equal extent. (iii) Antiserum against 30S subunits also has the property of precipitating both 30S and 70S ribosomes. The differences in the structural organisation of the two subunits may account for the differences in their immunoprecipitability. © 1980 Indian Academy of Sciences.
Incorporation of 5S RNA into 16S·23S RNA complex
(1983) D.S. Tewari; D.P. Burma
5S RNA as such is not incorporated into 16S·23S RNA complex formed under reconstitution condition. However, the addition of 50S ribosomal proteins, L5, L18 and L25 L15 results in its incorporation in stoichiometric amount. None of the proteins added individually is capable of incorporating 5S RNA into the complex. Of the different combinations in pairs that are possible out of the four proteins, the pairs L5, L18 and L15, L18 stimulate the incorporation to some extent. Of the four possible triplets, L5, L18, L25 or L5, L15, L18 is the most efficient for maximum incorporation of 5S RNA. The presence of all the four proteins is no more effective than the combinations of the three. © 1983.
Interconversion of tight and loose couple 50 S ribosomes and translocation in protein synthesis
(1985) D.P. Burma; A.K. Srivastava; S. Srivastava; D. Dash
[No abstract available]
Intermittent right bundle branch block due to digitoxin toxicity - A rare electrocardiographic manifestation
(1983) S. Sundar; P. Avasthey; D.P. Burma; S.K. Vaish
[No abstract available]
Mechanism of ribosomal subunit association: oligodeoxynucleotides as probes.
(1992) R.K. Agrawal; A. De; D.P. Burma
From the kethoxal treatment data [Herr, W.; Chapman, N.M.; Noller, H.F. (1979) J. Mol. Biol. 130, 433-439] some regions of ribosomal RNAs are thought to be responsible for the association of 30S and 50S ribosomes of E. coli to form 70S ribosomes. In order to test this possibility about a dozen oligodeoxynucleotides complementary to the suspected regions of rRNAs were synthesised. Their association with ribosomes and naked rRNAs was tested by the gel filtration technique. In order to check the effects on the ribosomal subunit association or rRNA association either intact 30S and 50S ribosomes or naked 16S and 23S rRNAs were preincubated with the individual oligodeoxynucleotide and its effect was checked by density gradient centrifugation followed by UV absorbance monitoring. Some oligodeoxynucleotides interfered with either subunit association or 16S RNA and 23S RNA association, some with both. These data clearly indicate that RNA-RNA interaction plays the major role in ribosomal subunit association.