Institutes
Refine
Year of publication
Document Type
- Article (311)
- Doctoral Thesis (236)
- Preprint (40)
- Book (9)
- Contribution to a Periodical (6)
- Review (4)
Has Fulltext
- yes (606)
Is part of the Bibliography
- no (606)
Keywords
- Podospora anserina (7)
- SARS-CoV-2 (7)
- Synechococcus (6)
- aging (6)
- 14CO2 Fixation (5)
- Haloferax volcanii (5)
- Phylogeny (5)
- Acetogenesis (4)
- Cyanobacteria (4)
- Ecology (4)
Institute
- Biowissenschaften (606) (remove)
Testosterone, Androst-4-en-3,17-dione, Enzyme Induction, S trep to m yces hydrogenans After cultivation of S trep to m yces hydrogenan s in the presence of 3H-labelled testosterone, radio active steroids were extracted separately from the cytosolic, ribosomal and cell wall-membrane fraction of the cells and from the culture medium, respectively.. The separation of the steroids was performed by one-and two-dimensional thin layer chromatography (TLC). The identification of the main metabolites was achieved by crystallization to constant specific radioactivity, specific staining procedures and acetylation. The oxidation of testosterone to androst-4-en-3,17-dione is by far the predominating reaction, which is almost finished after 3 h cultivation. Androst-4-en-3,17-dione is mainly transferred into the culture medium and partly accumulated within the cell wall-membrane fraction. High polar steroid metabolites and androstane derivatives are present in very small amounts only.
In haploid and diploid S. cerevisiae the dimer yield ratio TT̂/CT̂ is found to be 1.2/1 and 1.3/1, resp., at the UV (254 nm) unit dose 1 erg/mm2, the share of TT̂ and CT̂ in a UV (254 nm) lethal hit being 0.7 TT̂ and 0.6 CT̂. A general formulation of the UV lethal hit is given and discussed. The TT̂ + CT̂ yields obtained for S. cerevisiae are compared to those reported for other organisms. It is found that there obviously exists a directly proportional linear correlation between genome size and TT̂ + CT̂ yield for the UV dose range well below the stationary levels of the TT̂ and CT̂ formation kinetics.
A screening procedure is presented which allows the isolation of yeast mutants (typ tlr) with highly efficient utilization of exogenous deoxythymidine-5′-monophosphate (5′-dTMP) (>50% ). Data are given concerning the phenomenon of 5′-dTMP utilization in general: (i) The ability of S. cerevisiae to incorporate exogenous 5′-dTMP was found to already be a wild type feature of this yeast, i. e. apparently not to be due to any mutation such as typ , tup, tmp per or tum. Consequently these mutations are interpreted as amplifiers of a pre-given wild type potency. So far eight stages of 5′-dTMP utilization were detected as classified by the optimal 5′-dTMP requirement, with 5′-dTMP biosynthesis blocked, of the corresponding mutant strains isolated. All of them fit well into a mathematical series of the type “2n × 1.5” (n = 0, 1, 2, … , 11), where the product term for n = 11 represents the 5′-dTMP requirement (μg/ml) of the best 5′-dTMP utilizing wild type strain found, (ii) Amplification of the 5′-dTMP utilizing potency obviously is due to any genetically determined alteration of the yeast 5′-dTMP uptaking principle itself or of physiological processes accompanying the monophosphate’s uptake, (iii) The functioning of 5′-dTMP uptake requires acidic (≦ pH 6) conditions in the yeast cell’s outer environment, (iv) Some yeast typ and typ tlr mutants were found to exhibit a more or less pronounced sensitivity towards exogenously offered 5′dTM P. The response of a sensitive strain towards inhibitory concentrations of the nucleotide apparently is co-conditioned by the presence or absence of thymidylate biosynthesis. With 5′-dTMP biosynthesis blocked the 5′-dTMP mediated inhibition is a permanent one and finally leads to the death of a cell. With a functioning thymidylate biosynthesis, in contrast, the inhibition is only temporary, (v) Yeast typ or typ tlr strains were observed to dephosphorylate exogenous 5′-dTMP to thymidine due to a phosphatase activity which cannot be eliminated at pH 7 + 70 mм inorganic phosphate conditions in the growth medium. This 5′-dTMP cleavage obviously occurs outside the cell and does not seem to be correlated both to the monophosphate’s uptake and to the phenomenon of 5′-dTMP sensitivity. The destruction of 5′-dTMP does not disturb (5′-dTMP) DNA-specific labelling.
The blue-green alga Anacystis nidulans (strain L 1402-1) was grown at + 37 °C in air (0.03 vol.% CO2 and in air enriched with 3.0 vol.% CO2. The effects of several inhibitors on the activity of aminotransferases, 14CO2 fixation and radioactive photosynthetic products of Anacystis were studied. No serine-pyruvate aminotransferase activity could be found in 10-2 м isonicotinyl hydrazide (INH) ; under the influence of this inhibitor aspartate and alanine aminotransferase were decreased about 49% respectively 17.6%. Serine-pyruvate and alanine aminotransferase activity decreased to more than 50% in 10-3 м glyoxalbisulfite. The obtained inhibitory effect of 10-4 м HPMS on serine-piruvate aminotransferase (35%) was stronger than on the other aminotransferases. DCMU (5 × 10-6 м) inhibition on alanine aminotransferase activity was 83.7%. Under the influence of 10-3 м glyoxalbisulfite no 14C-labelled amino acids could be detected after 5 min photosynthesis; 14C-labelling of phosphoenolpyruvate, malate, phosphoglycolate and glycolic acid increased. Isonicotinyl hydrazide (10-2 м) caused in comparison to the control experiment a lower radioactivity in aspartate, glutamate and phosphoenolpyruvate. The results are discussed with reference to the operation of the glycolate pathway and a carboxylation reaction of phosphoenolpyruvate in the blue-green alga Anacystis nidulans.
Chromatin, RNA Polymerase, Potato Tuber Tissue, Aging Phenomenon The synthesis of RNA by chromatin-bound RNA polymerase (E.C. 2.7.7.6.) from white potato tubers proceeds at a low rate, which is enhanced after slicing the tissue, however. Concomitantly DNA template availability as measured with saturating amounts of Escherichia coli polymerase is diminished drastically. Nearest neighbor frequency analysis proved that the RNA synthesized on chromatin of intact tubers is different from that synthesized on chromatin of sliced tissue.
The RNA polymerase of white potato tubers is dependent on all four ribonucleoside triphos phates and a divalent metal ion such as Mg2+ or Mn2+ and totally inhibited by the presence of pyrophosphate. Actinomycin D blocks the formation of the RNA product, which could be shown to be a heteropolymer by nearest neighbour frequency technique. The Km of the chromatin-bound enzyme with regard to ATP, GTP, CTP and UTP was 5.1 X10-5 M, 1.6X10-5 M, 0.9X10-5 M and 0.45 X 10-5M/1 respectively, α-amanitin inhibits the overall activity to about 50%, which indicates the presence of equal amounts of polymerase I and polymerase If.
Phosphoenolpyruvate carboxykinase (PEPCK) from Phycomyces blakesleeanus was partially purified by protamine sulfate precipitation, ammoniumsulfate precipitation, and diethylamino ethyl cellulose (DEAE) treatment. This preparation was employed for the characterization of the enzyme. The Km values for phosphoenolpyruvate (PEP) and ADP were determined as 1.6 and 0.42 mᴍ. The nucleotid specifity was demonstrated for ADP exclusively. The use of sulfuryl reagents showed the presence of thiol groups sensitive against p-hydroxymercuribenzoate but not effected by N-ethylmaleimide.
A quantitative determination method of gallic and protocatechuic acid in cultures and liquid nutrient of Phycomyces blakesleeanus was described. Both phenolic acids were separated by TLC and the colour reaction with Folin reagent was used for a colorimetric test. This procedure was employed for investigating the formation of gallic and protocatechuic acid in cultures with optimal (10-4 m) and reduced (1.3 × 10-6 ᴍ) zinc supply showing that their production is stimulated by zinc ions.
In addition, the inhibiting effect of light on the accumulation of gallic acid was manifested, however, its excretion into the medium was uneffected by light and protocatechuic acid was not excreted at all. During the development of Phycomyces gallic and protocatechuic acid could be detected in two days old mycelium . With the sporangiophore production both acids are accumulated more rapidly in the sporangiophores. After the end of sporangiophore formation the gallic acid content increases only slightly. In contrast the total content of protocatechuic acid decreases sharply. As no excretion occurs a degradation of at least protocatechuic acid must be taken into consideration.
The cyanobacterium Synechococcus (Anacystis nidulans strain L 1402-1) was grown at + 37 °C in 3.0 vol.% CO2. The effect of preillumination with white light on the subsequent dark 14CO2 fixation was studied under aerobic conditions at + 30 °C. The radioactive carbon first incoiporated into 3-phosphoglyceric acid was transferred during the later periods of dark 14CO2 fixation to phosphoenolpyruvate and aspartate. No labelling or a very low label in sugar monophosphates could be observed. During the dark/light transients the initial fixation product was mainly aspartate. The pattern of 14C-incorporation into photosynthetic products under steady state conditions (10 min photosynthesis) varied with the temperature during the experiments. The radioactive carbon was firstly incorporated into 3-phosphoglyceric acid. During the later periods of photosynthetic 14CO2 fixation an increased 14C-incorporation into aspartate and glutamate could be observed. Our findings were interpreted with operating of a phosphoenolpyruvate carboxylation besides the Calvin cycle.
A thylakoid membrane preparation isolated from the blue-green alga Anacystis nidulans was freed from carboxysomes, soluble enzymes and the pigment P750 by floating in a discontinuous sucrose density gradient. In a buffer containing sucrose and the zwitterionic detergent Miranol S2M-SF the thylakoids were loaded on a linear 10-18% sucrose density gradient which also contained Miranol. The sedimentation yielded three bands, the lower two of which were green and the upper one was orange. The light green band in the middle of the gradient was the only one to show any photosystem II activity. This was measured as light-induced electron transport from diphenylcarbazide (DPC) to dichlorophenol-indophenol (DCPIP). The activity was sensitive to dichlorophenyl-dimethylurea (DCMU).
The red absorption maximum of the particles in this middle band - henceforth called photosystem II particles - was found at 672 nm and the maximum of their low temperature fluorescence emission spectrum at 685 nm upon excitation with blue light. Cytochrome b559 was the only cytochrome found in these particles; it was present at an average ratio of one molecule cytochrome per 40 -50 molecules chlorophyll a. C550 photoreduction with accompanying photooxidation of cytochrome b559 was also observed in the photosystem II particles. Good photosystem II preparations did not contain any detectable amounts of P 700.
By means of sodium dodecylsulfate polyacrylamide gel electrophoresis the polypeptide composition of the photosystem II particles was studied. Dissolution of the chlorophyll protein complexes was done under strongly denaturing conditions; consequently, no green bands were observed on the gels. The polypeptide pattern of the photosystem II particles showed two strong predominant bands of protein components with apparent molecular weights (app. mol. wts.) of about 50 000 and 48 000. These two bands are unique for photosystem II. Two other weaker bands were also found characteristic for photosystem II, the band of a polypeptide with an app. mol. wt. of 38 000 and that of a polypeptide with an app. mol. wt. of 31 000. Sometimes in addition the weak band of a polypeptide with the app. mol. wt. 27 000 was observed on the gel. The polypeptide 38 000 aggregated upon boiling of the sample in the presence of the denaturing agents prior to the electrophoresis, yielding an aggregate with an app. mol. wt. of 50 000. Additional polypeptides which were often found in the photosystem II particle preparation could be identified as subunits of the coupling factor of photophosphorylation CF1. None of the polypeptides described as characteristic for photosystem II are due to proteolytic activity.
As the observed photosystem II activity was found to be DCMU-sensitive it appears that the DCMU-binding protein is among the here described photosystem II polypeptides. Moreover, the authors have reason to believe that one of the major protein components found characteristic for photosystem II is cytochrome b559.
The cyanobacterium Synechococcus (Anacystis nidulans strain L 1402-1) was grown at +35 °C in air and in air enriched with 2.2 vol.% CO2. The effect of different oxygen concentrations (0, 2, 20, 50, 75 and 99.97 or 97.8 vol.%) was studied in low (0.03 vol.%) and high (2.2 vol.%) CO2 concentrations at + 35 °C. After exposure to a nitrogen atmosphere and low CO2 content I4C-bicarbonate was mainly incorporated into aspartate and glycine/serine. During oxygenic photosynthetic CO2 fixation label in aspartate decreased and a high degree of radioactivity could be found in 3-phosphoglyceric acid and sugar monophosphates. The Calvin cycle was the main fixing pathway in 2.2 vol.% CO2 during anoxygenic and oxygenic conditions independent on the O2 concentrations during the experiments. No oxygen enhancement of photosynthetic CO2 fixation could be found. Possible mechanism involved in CO2 fixation pathways and glycolate metabolism underlying the effect of oxygen was discussed.