Primary haemangiosarcoma of the tongue.
A 52-year-old male had a biopsy done from a tongue lesion and was reported to have primary haemangiosarcoma. The case has been reported because of the rarity of this tumour.
Hemangiosarcoma↗
Biomedical subjects
K K Rao
Publications and source records attributed to K K Rao.
Effects of alterations in cellular iron on biosynthesis of the transferrin receptor in K562 cells.
Treatment of K562 cells, a human erythroleukemia cell line, with desferrioxamine raised the levels of the receptor for transferrin (Tf) two- to threefold over that of the control cells. The levels of receptor were reduced by at least 50 and 35% of that of the control in cells treated with diferric Tf and ferric ammonium citrate, respectively. These changes were of total cellular receptors with no alteration in the proportion of receptors found on the cell surface. The half-lives of the receptor were identical in cells treated with desferrioxamine, diferric Tf, or ferric ammonium citrate. Cells metabolically labeled with [35S]methionine showed a 2.5-fold increase in the rate of receptor synthesis when treated with desferrioxamine and a 35 and 65% decrease when treated with ferric ammonium citrate and diferric Tf, respectively. In vitro translations of polyadenylated mRNA isolated from cells incubated with desferrioxamine showed a 2.5-fold increase in translatable mRNA for the receptor, whereas treatment of cells with ferric ammonium citrate and diferric Tf resulted in a 25 and 50% reduction, respectively, in translatable mRNA for this receptor.
Cell Line↗
Basic characterization of a Pseudomonas aeruginosa PAO1 bacteriophage.
A bacteriophage of Pseudomonas aeruginosa PAO1 was characterized. Bacteriophage PIK was found to adsorb on the cell wall of the host organism. Electron microscopy of the phage PIK revealed that it had a bipyramidal hexagonal prismatic head of 110 nm in diameter, a tail which was 158 nm long and a tail plate of 47 nm width. This paper describes its basic characters, and a quantitative study was made of its adsorption to exponential phase cells of two different strains of P. aeruginosa. PIK was found to contain double stranded DNA and it appears to be virulent towards its host, P. aeruginosa PAO1. It was classified into the group of phages possessing a contractile tail.
Acridine Orange↗
Spectroscopic studies of the nature of the iron clusters in the soluble hydrogenase from Desulfovibrio desulfuricans (strain Norway 4).
57Fe-enriched samples of the soluble hydrogenase from Desulfovibrio desulfuricans (Norway) have been investigated in both the native (oxidized) and the dithionite-reduced states using Mössbauer spectroscopy. The data clearly show that the iron in this enzyme is predominantly in the form of iron-sulphur clusters which are closely similar to the [4Fe-4S] clusters found in a large number of ferredoxins, such as that from Bacillus stearothermophilus. There appear to be two [4Fe-4S] clusters. The iron-sulphur clusters in the oxidized protein are virtually diamagnetic, as indicated by Mössbauer, electron spin resonance and magnetic circular dichroic spectroscopy. On reduction by dithionite + methyl viologen, Mössbauer spectroscopy showed that only 50% of the [4Fe-4S] clusters were reduced. Even reduction with hydrogen up to a pressure of 23 GPa did not reduce the iron-sulphur clusters completely. An ESR signal due to a rapidly relaxing species with g = 2.03, 1.89 was observed in the reduced protein, together with a weaker spectrum from a slower-relaxing species at g = 2.34, 2.12.
Chemical Phenomena↗
Prophage induction by liver microsomal metabolites of aflatoxin B1 in lysogenic Pseudomonas aeruginosa.
Microsomal metabolites of aflatoxin B1 (AFB1) causing induction of prophage in lysogenic strain of Pseudomonas aeruginosa SM was studied. Reduction of culture turbidity was determined at various concentrations of toxin. The effect of the toxin was also studied on deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and protein synthesis. AFB1 at the concentration of 50 micrograms/ml reduced initial turbidity to approximately 90% in 4 h. DNA synthesis stopped completely in the first hour but reappeared due to induction of the temperate phage. Soon after induction both RNA and protein synthesis continued but later little or no net synthesis of these macromolecules occurred. Plaque forming units (pfu) were increased approximately 90 times at 2 h as compared to the control. Testing of the effect of AFB1 on the non-lysogenic, sensitive strain demonstrated that although there was no significant decrease in culture turbidity at 50 micrograms/ml concentration of AFB1, DNA synthesis stopped completely within 1 h, while RNA and protein synthesis were increasing throughout the test interval. It has been concluded that the liver microsomal fraction of AFB1 caused induction of prophage in lysogenic cells and inhibited DNA synthesis significantly in non-lysogenic cells.
Aflatoxin B1↗
Kinetic studies on reactions of iron-sulphur proteins. Oxidation of the reduced form of Spirulina platensis [2Fe-2S] ferredoxin with inorganic complexes.
Kinetic results are presented for the reaction of reduced [2Fe-2S] ferredoxin from the blue-green alga Spirulina platensis with Co(NH3)6(3+), Co(edta)- and Co(acac)3 as oxidants at pH 8.0 at I0.10 (NaCl). The aim is to compare results obtained with those previously reported for the [2Fe-2S] ferredoxin from parsley, where the two ferredoxins under consideration are in evolutionary terms widely divergent (35% amino acid variations). The three oxidants chosen have different ligand sets and different charges, and are the complexes that in previous studies have given greatest diversity in behaviour. With Co(NH3)6(3+) first-order rate constants (oxidant in large excess) tend to a limiting value with increasing concentration of oxidant. With Co(edta)- and Co(acac)3 there is no similar tendency to limiting behaviour and a first-order dependence on oxidant is observed. The temperature-dependence of the Co(NH3)6(3+) reaction was investigated, and values were obtained for delta H0 [19.8kJ X mol-1 (4.7kcal X mol-1)] and delta S0 [129.3J X K-1 X mol-1 (30.9 cal X K-1 X mol-1)] for the association step that occurs before electron transfer. Whereas redox-inactive Cr(NH3)6(3+) displays competitive inhibition in the reaction of Co(NH3)6(3+), it accelerates the reaction of Co(edta)-, and only partially blocks the reaction with Co(acac)3. Results obtained are similar to those previously reported for parsley (and spinach) ferredoxin. It is concluded that electrostatics play a dominant role and that a negatively charged functional site on the protein common to all three ferredoxins is influential. Conserved negative patches at positions 67-69 and 94-96 within 1.0 nm (10A) of an Fe atom of the active site, as well as the exposed S atoms of cysteine residues 41 and 46, which are a part of the Fe2S*2(SR)4(3-) cluster, are the most likely possibilities. The various effects of Cr(NH3)6(3+) provide a means of testing for utilization of the same site in reactions of the ferredoxins with physiological partners.
Cobalt↗
Purification and properties of the membrane-bound by hydrogenase from Desulfovibrio desulfuricans.
The membrane-bound hydrogenase from the anaerobic sulphate-reducing bacterium Desulfovibrio desulfuricans (Norway strain) has been purified to homogeneity, with an overall 80-fold purification and a specific activity of 70 mumol of H2 evolved/min per mg of protein. The hydrogenase had a relative molecular mass of 58 000 as determined by gel filtration and was estimated to contain six iron atoms and six acid-labile sulphur groups per molecule. The absorption spectrum of the enzyme was characteristic of an iron-sulphur protein. The E400 and E280 were 28 500 and 109 000 M-1.cm-1 respectively. The e.s.r. of the oxidized protein indicated the presence of [4Fe-4S]3+ or [3Fe-3S]3+, and another paramagnetic centre, probably Ni(III). The hydrogenase was inhibited by heavy-metal salts, carbon monoxide and high ionic strength. However, it was resistant to inhibition by thiol-blocking and metal-complexing reagents. N-Bromosuccinimide totally inhibited the enzyme activity at low concentrations. The enzyme was stable to O2 over long periods and to high temperatures. It catalyses both H2-evolution and H2-uptake with a variety of artificial electron carriers. D. desulfuricans cytochrome C3, its natural electron carrier, had a high affinity for the enzyme (Km = 2 microns). Rate enhancement was observed when cytochrome C3 was added to Methyl Viologen in the H2-evolution assay. The pH optimum for H2-evolution was 6.5.
Amino Acids↗
Studies on the Pseudomonas aeruginosa PAO1 bacteriophage receptors.
Receptor for phage PIK specific for Pseudomonas aeruginosa strain PAO1 was studied. Phage PIK was strongly inactivated by lipopolysaccharide (LPS) in vitro, exhibiting a PhI50 of 4.8 micrograms/ml. Further it was noted that this inactivation by LPS was reduced to 50% by several mono- and disaccharides when tested in vitro. D-glucosamine, D-mannose and L-rhamnose were found to be most effective at the concentration of 0.045 M, 0.25 M and 0.35 M respectively. This suggests the possibility that phage PIK receptor in LPS contains D-mannose, L-rhamnose and D-glucosamine. Either one of the former two could be located at a terminal position alpha-linked to the adjacent residue or located internally in the polysaccharide chain linked through its C-4 position. A theoretical approach to the interpretation of phage cell interaction was also investigated.
Adsorption↗
Mössbauer spectroscopic evidence for the conversion of [4 Fe--4 S] clusters in Bacillus stearothermophilus ferredoxin into [3 Fe--3 S] clusters.
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Ferredoxins↗
Identification of inner- and outer-sphere reaction pathways in the reduction of iron-sulphur proteins with a chromium (II)-macrocycle complex.
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Chromatium↗
Low-temperature magnetic circular dichroism spectra and magnetisation curves of 4Fe clusters in iron-sulphur proteins from Chromatium and Clostridium pasteurianum.
The magnetic circular dichroism (MCD) spectra of the 4Fe clusters in the iron-sulphur proteins high-potential iron protein from Chromatium and the 8Fe ferredoxin from Clostridium pasteurianum have been measured over the wavelength range 300-800 nm at temperatures between approx. 1.5 and 50 K and at magnetic fields up to 5 tesla. In both cases the proteins have been studied in the oxidized and reduced states. The reduced state of high-potential iron protein gives a temperature-independent MCD spectrum up to 20 K, confirming the diamagetism of this state at low temperature. The MCD spectrum of samples of oxidized ferredoxin invariably show the presence of a low concentration of a paramagnetic species, in agreement with the observation that the EPR spectrum always shows a signal at g = 2.01. The paramagnetic MCD spectrum runs across the whole of the wavelength range studied and therefore most probably originates from an iron-sulphur centre. The diamagnetic component of the MCD spectrum of oxidized ferredoxin is very similar to that of reduced high-potential iron protein. The low-temperature MCD spectra of oxidized high-potential iron protein and reduced ferredoxin reveal intense, temperature-dependent bands. The spectra are highly structured with that of high-potential iron protein showing a large number of electronic transitions across the visible region. The MCD spectra of the two different oxidation levels are quite distinctive and should provide a means of establishing the identity of these state of 4Fe clusters in more complex proteins. MCD magnetisation curves have been constructed from detailed studies of the field and temperature dependence of the MCD spectra of the two paramagnetic oxidation states. These plots can be satisfactorily fitted to the theoretically computed curves for an S = 1/2 ground state with the g factors experimentally determined by EPR spectroscopy. The low-temperature MCD spectra of the reduced 2Fe-2S ferredoxin from Spirulina maxima are also presented and MCD magnetisation curves plotted and fitted to the experimentally determined g factors.
Chromatium↗
Metalloproteins in the evolution of photosynthesis.
Certain metalloproteins are common to all photosynthetic electron transfer chains. These include soluble proteins such as ferredoxins and cytochromes of the c2 type, and membrane-bound components such as cytochrome b, c1 and the Rieske iron-sulphur protein. The sequence of electron transfer Quinone leads to (cyt b, Fe-S, cyt c1) leads to cyt c2 indicates a common precursor to these systems and to the mitochondrial respiratory chain. In cyanobacteria the cytochrome c2 can be interchanged with the copper protein plastocyanin, and furthermore in chloroplasts of higher plants the latter is used exclusively. The ferredoxins in anaerobic photosynthetic bacteria are mostly of the [4Fe-4S] type, probably derived from those of the fermentative bacteria. These could readily be formed in the earliest cells from iron, sulphide and a very simple peptide. In the oxygen-evolving cyanobacteria and the aerobic halobacteria the [2Fe-2S] ferredoxins predominate. The electron transfer chains of the cyanobacteria have been incorporated almost unchanged into the chloroplasts of plants. The electron transfer chains of purple photosynthetic bacteria were probably the precursors of the mitochondrial respiratory chain, as shown by similarities of cytochromes c2 and succinate dehydrogenase. However a different origin of the eukaryotic cytoplasm is indicated by the presence of the copper/zinc superoxide dismutase.
Amino Acid Sequence↗
Isolation of two hydrogenase activities in Chromatium.
Kinetic, chromatographic and electrophoretic studies of Chromatium hydrogenase show the existence in vitro of two different activities (I and II). The two hydrogenases exhibit different kinetic parameters and properties. Using reduced methyl viologen, Km and [S]0.5 values of about 20 microM and 360 microM were calculated for the hydrogenases I and II, respectively. Hill plots revealed that hydrogenase I followed classical hyperbolic (Michaelis-Menten) kinetics. However, a Hill coefficient (h = 0.68) indicating non-hyperbolic kinetics could be shown for hydrogenase II. After several purification steps hydrogenase II still showed kinetics typical of the action of either (a) two enzymes each of which shows Michaelis-Menten kinetics but with different substrate affinities or (b) only one enzyme which shows apparent negative cooperative regulation. The molecular weights of the hydrogenases were about 37,000 (I) and 55,000 (II) when determined by gel filtration. Sodium dodecyl sulphate/polyacrylamide gel electrophoresis revealed that both enzymes give a coincidental single protein band with the same relative mobility indicating a molecular weight of 31,000. Both hydrogenases were able to catalyse the reversible activation of H2 in the presence of artificial electron carriers but with different rates, hydrogenase II being much more active in the H2-uptake mode. The kinetic properties and molecular weight of hydrogenase II are partially modified by high ionic strength resulting in an increased substrate affinity and Hill coefficient and thus resembling hydrogenase I. These results are interpreted as due to the existence in vitro of monomeric and dimeric forms of Chromatium hydrogenase.
Chromatium↗
Efficiency of ferredoxins and flavodoxins as mediators in systems for hydrogen evolution.
1. The efficiencies of ferredoxins and flavodoxins from a range of sources as mediators in systems for hydrogen evolution were assessed. 2. In supporting electron transfer from dithionite to hydrogenase of the bacterium Clostridium pasteurianum, highest activity was shown by the ferredoxin from the cyanobacterium Chlorogloeopsis fritschii and flavodoxin from the bacterium Megasphaera elsdenii. The latter was some twenty times as active as comparable concentrations of Methyl Viologen. Ferredoxins from the cyanobacterium Anacystis nidulans and the red alga Porphyra umbilicalis also showed high activity. 3. In mediating electron transfer from chloroplast membranes to Clostridium pasteurianum hydrogenase the flavodoxin from Anacystis nidulans proved the most active with Nostoc strain MAC flavodoxin and Porphyra umbilicalis ferredoxin also being appreciably more active than other cyanobacterial and higher plant ferredoxins. 4. In both hydrogenase systems the ferredoxin and flavodoxin from the red alga Chondrus crispus and the ferredoxin from another red alga Gigartina stellata showed very low activity. 5. There appeared to be no apparent correlation of efficiency in supporting hydrogenase activity with midpoint redox potential (Em) of the mediators, though some correlation of Em with the efficiency of the mediators in supporting NADP+ photoreduction by chloroplasts, or pyruvate oxidation by a Clostridium pasteurianum system, was evident. 6. Activity of the mediators in the hydrogenase systems therefore primarily reflects differences in tertiary structure conferring differing affinities for the other components of the systems.
Bacteria↗
Antiferromagnetic exchange interaction in the two-iron-two-sulphur ferredoxin from the blue-green alga Spirulina maxima studied with a highly sensitive magnetic balance.
1. A highly sensitive magnetic balance of the Faraday type is described. 2. The magnetic susceptibility of the oxidized and reduced forms of the two-iron-two-sulphur ferredoxin from the blue-green alga Spirulina maxima has been measured over a wide temperature range. 3. The results can be interpreted within a simple model involving antiferromagnetically coupled iron atoms at the active site. The coupling, expressed as --J, is estimated to be 182 +/- 20/cm and 98 +5/-10 /cm for the oxidized and reduced forms, respectively.
Binding Sites↗
Biological activity of synthetic molybdenum-iron-sulphur, iron-sulphur and iron-selenium analogues of ferredoxin-type centres.
The molybdenum-iron-sulphur cluster [Fe6Mo2S8(SCH2CH2OH)9]3-, which contains two Fe3MoS4 cubane-like centres, is the best plausible analogue available to date for the molybdenum site of the nitrogenase enzymes. The iron-sulphur cluster [Fe4S4(S . CH2CH2OH)4]2- and the iron-selenium cluster [Fe4Se4(S . CH2CH2OH)4]2- are structural analogues of the ferredoxin Fe4S4 active centre. All three clusters would replace ferredoxin and mediate electron transfer to Clostridium pasteurianum hydrogenase in a H2-evolving system with sodium dithionite as the electron donor. The clusters would not replace hydrogenases which themselves are unable to evolve H2 from reduced ferredoxins. The molybdenum-iron-sulphur cluster would also replace ferredoxin in a chloroplast-ferredoxin-hydrogenase H2 evolving system.
Binding Sites↗
Cellulase induction in Aspergillus fumigatus M 216.
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Aspergillus fumigatus↗