bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distance Measurement by Energy Transfer: The 3′ End of 16‐S RNA and Proteins S4 and S17 of the Ribosome of Escherichia coli
Authors: EPE Bernd , WOOLLEY Paul , STEINHÄUSER Klaus G. , LITTLECHILD Jennifer 
Published: March 2005

Escherichia coli ribosomal proteins S4 and S17 were specifically labelled at their thiol groups with the acetylaminoethyl‐dansyl and/or bimane fluorophores. Each formed a complex with 16‐S RNA and, when the other 30‐S ribosomal proteins were added, a complete 30‐S subunit with at least partial activity. If the 3′ end of the RNA was also labelled (with fluorescein) then the distance between the two fluorophores could be measured by Förster‐type energy transfer. The result for S4 was 6.0 nm (60 Å) in the ribonucleoprotein complex and 5.6 nm (56 Å) in the 30‐S subunit, and for S17 6.3 nm (63 Å) in the complex and 6.2 nm (62 Å) in the subunit. There is no evidence for a major change in the relative disposition of the 3′ and 5′ ends of the 16‐S RNA during formation of the 30‐S subunit. Sources of error are discussed, including the question of multiple labelling.In order to measure more accurately the extent of energy transfer a procedure based upon enzymic digestion was developed and is detailed in this paper.
Component E of the DNA‐Dependent RNA Polymerase of the Archaebacterium Thermoplasma acidophilum Is Required for the Transcription of Native DNA
Authors: SCHNABEL Ralf , ZILLIG Wolfram , SCHNABEL Heinke 
Published: March 2005

The role of component E of the DNA‐dependent RNA polymerase of the archaebacterium Thermoplasma acidophilum in the transcription of Thermoplasma DNA has been analyzed.Component E (Mr 22000) is released upon formation of the binary complex of the polymerase with the DNA. Enzyme not containing component E is inactive on DNA but active on poly[d(A‐T) · d(A‐T)]. The activity on DNA can be restored by addition of component E.Two states of the binding complex between RNA polymerase and DNA, differing in their tonic strength stabilities, have been distinguished both in the presence and absence of component E. between the two states is 43°C.Component E appears to open productive binding sites in native DNA in addition to the non‐productive strong binding sites available for component‐E‐deficient enzyme.
Purification and Properties of a d‐Galactose/N‐Acetyl‐d‐ galactosamine‐Specific Lectin from Erythrina cristagalli
Authors: IGLESIAS Jose L. , LIS Halina , SHARON Nathan 
Published: March 2005

The lectin from the seeds of Erythrina cristagalli has been isolated in high yield (75 %) and homogeneous form by affinity chromatography on a column of D‐galactose‐derivatised Sepharose. It is a glycoprotein with a molecular weight of 56800±900 and s20.w, = 3.9 S, composed of two subunits (apparent molecular weights of 28000 and 26000 respectively) both of which are glycosylated. The total carbohydrate content is 4.5% and it is comprised of mannose, N‐acetylglucosamine, fucose and xylose in amounts corresponding to 7, 4, 2 and 2 mo1/56800 Da respectively. The amino acid composition of the lectin is characterised by a high content of acidic and hydroxy amino acids, low content of methionine and absence of cysteine. Valine is the only N‐terminal amino acid detected. The lectin is a metalloprotein in that it contains 0.093% Mn and 0.13percnt; Ca (1 mol and 1.9 mo1/56 800 Da respectively), both of which are tightly bound to the protein. E. cristagalli lectin agglutinates untreated human erythrocytes of all blood types, as well as rabbit erythrocytes, at a concentration of 5‐10 μg/ml. It is mitogenic for human peripheral blood T lymphocytes at an optimal concentration of about 100 pμg/ml, but is not mitogenic for mouse thymocytes or splenocytes. d‐GahtOSe and various d‐galactosides inhibit the hemagglutinating activity of the lectin. N‐Acetyllactosarnine is most potent, completely inhibiting four agglutinating units of the lectin at 0.4 mM concentration. Lactose, N‐acetyl‐d‐galactosamine and d‐galactose are 5, 16 and 35 times less active respectively. Lactose specifically perturbs the ultraviolet spectrum of the lectin in the aromatic region. The difference spectrum obtained upon binding of the disaccharide to the lectin shows maxima at 291 nni and 282‐284 nm, indicating a change in the environment of tryptophan residues of the protein upon binding of sugar.
A Sphingomyelin Transfer Protein in Rat Tumors and Fetal Liver
Authors: DYATLOVITSKAYA Ella V. , TIMOFEEVA Natalya G. , YAKIMENKO Ekaterina F. , BARSUKOV Leonid I. , MUZYA Galina I. , BERGELSON Lev D. 
Published: March 2005

Affinity resins containing covalently bound phospholipids were used to compare the affinity of the phosphatidylcholine transfer protein from beef liver and a low‐specificity lipid transfer protein from rat hepatoma 27 to phosphatidylcholine and sphingomyelin. Binding experiments demonstrated that the beef liver protein associates specifically with immobilized phosphatidylcholine whereas the hepatoma protein showed a preference for sphingomyelin.Purified antiserum raised against the hepatoma sphingomyelin transfer protein was used to determine the presence of that protein in the cytosol of various experimental tumors as well as in those of normal, regenerating and fetal rat liver. The protein was found to be well expressed in all the tumors examined and in fetal liver as determined by immunodiffusion whereas only minute amounts could be detected in normal liver and in 30‐h regenerated liver. The presence of the sphingomyelin transfer protein in cytosol was in parallel with the presence of sphingomyelin in the corresponding mitochondria. It is suggested that the occurrence of sphingomyelin in tumor and fetal liver mitochondria may be due to protein‐catalyzed sphingomyelin transfer from the endoplasmic reticulum.
Dual Control of Phenyladanine Ammonia‐Lyase Production and Removal by Its Product Cinnamic Acid
Authors: SHIELDS Susan E. , WINGATE Vincent P. , LAMB Christopher J. 
Published: March 2005

l‐Phenylalanine ammonia‐lyase (EC 4.3.1.9, which catalyses the first reaction in the biosynthesis of plant phenylpropanoid products, undergoes a transient increase in activity in excised sections of pea (Pisum sativum) epicotyl tissue. Exogenous supplies of pathway intermediates inhibit the initial development of phenylalanine ammonia‐lyase activity and, if added at the time of high enzyme levels, cause a rapid decay in enzyme activity. The inhibitory effect of exogenous cinnamic acid, the immediate product of the enzyme, is expressed very rapidly (lag < 1 h) with the initial rate of decay of enzyme activity and the final steady‐state level of enzyme activity being dependent on the concentration of cinnamic acid.The response has been studied by density labelling in vivo with 2H from 2H2O with analysis of the equilibrium distribution of enzyme activity in high‐resolution KBr density gradients. Cinnamic acid, at a concentration of 1 mM completely inhibits further incorporation of label and also markedly stimulates the removal of pre‐existing, unlabelled enzyme. Inhibition of de novo production and stimulation of removal occur at concentrations of cinnarnic acid as low as 10 μM.The initial increase in enzyme activity reflects an increase in the rate of de novo enzyme production against a low background rate of enz:yme removal. The subsequent decay in enzyme activity is a result of a decline in production of the enzyme concomitant with a marked increase in the rate of removal of enzyme activity. In the presence of α‐ aminooxy‐β‐phenylpropionic acid, which specifically inhibits phenylalanine ammonia‐lyase and hence endogenous generation of cinnamic cid, high rates of enzyme production and low rates of enzyme removal are maintained leading to high levels of zyme activity in the later stages of enzyme induction. These data indicate the operation of dual feedback modulation of phenylalanine ammonia‐lyase in vivo following endogenous production of cinnamic acid. Such dual control by a product over both production and removal of an enzyme may be of general importance in slowly growing plant cells for the rapid removal of biosynthetic enzymes no longer required by the cell.
Heterogeneous Distribution of ATP Citrate Lyase in Rat‐Liver Parenchyma
Authors: KATZ Norbert R. , FISCHER Wilhelm , ICK Margit 
Published: March 2005

A radiochemical microtest was established for the determination of ATP citrate lyase in tissue samples of 0.2–1.0 μg dry weight. The specificity of this test system was guaranteed by its coenzyme A dependence as well as by inhibition of the activity measured in presence of a specific antibody.
Using this test system ATP citrate lyase activity was determined in microdissected periportal and perivenous liver tissue of fed, fasted and refed animals. The perivenous activity was 1.8‐fold and 2.4‐fold higher than the periportal one in fed male and female rats respectively.
The perivenous to periportal gradient was decreased during starvation‐dependent reduction of the ATP citrate lyase activity. On the other hand it was not only restored but enhanced up to 2.8 after refeeding‐dependent enhancement of the enzyme activity.
The predominance of the ATP citrate lyase activity in the perivenous, mainly glycolytic zone supports the hypothesis of the coordinate zonation of the carbohydrate and the lipid metabolism in the liver parenchyma.
Rotational Motion of Actin Monomer at Low and High Salt Concentration
Authors: BELÁGYI József , GRÓF Pál 
Published: March 2005

Treatment of F‐actin pellet with 1 M MgCl2 results in a high concentration of monomer actin in solution [Biró, E. N. A. and Venyaminov, S. Yu. (1979) Acta Biochim. Biophys. Acad. Sci. Hung. 14, 31–42]. The physico‐chemical properties of this actin solution were studied by the spin‐labelling method and were compared with the normal actin solutions. The electron paramagnetic resonance (EPR) spectra produced the following results.

The rotational correlation time for monomer actin at low ionic strenght, which was calculated by the extrapolation procedure, increased from 16 ns to 26 ns in the presence of 1 M MgCl2.
The polymerization of actin is accompanied by a change in the polarity of the environment of the label (increasing hydrophobicity).
When heavy meromyosin (HMM) was added to monomer actin at high ionic strengh, the EPR data provided evidence that HMM induced the polymerization of the MgCl2‐depolymerized actin.
The Reactivity of Arginine Residues Interacting with Glucose 1‐Phosphate in Glycogen Phosphorylase
Authors: VANDENBUNDER Bernard , BUC Henri 
Published: March 2005

Modification of pyridoxal‐reconstituted phosphorylase b with two arginine‐directed reagents, butanedione and [14C]phenylglyoxal, has been investigated and compared with the results obtained on the active and inactive conformations of the native enzyme; the reactivity of the various arginine residues has been directly described using autoradiography of chymotryptic maps derived from [14C]phenylglyoxal‐labelled phosphorylase.In the native enzyme this method demonstrates that the same arginine residue (568) is reactive on both activated phosphorylase a and b, non‐reactive on inactive forms of phosphorylase and protected by glucose 1‐phosphate. Another residue is reactive, but its reactivity does not drastically depend upon phosphorylase conformation; it interacts with glucose 1‐phosphate.In the pyridoxal‐reconstituted phosphorylase, the residue Arg‐568 is reactive. This reactivity does not correlate in a simple manner with the ionisation state of the coenzyme, since it is high when this group is either absent or in a dianionic form, and low when it is monoanionic. The reactivity of Arg‐568 rather correlates with the quaternary structure of the enzyme. The protection offered by glucose 1‐phosphate, pyrophosphate and phosphite on this pyridoxal‐reconstituted phosphorylase also provides information about the relative disposition of the substrate, the coenzyme and this particular arginine residue.
Ca2+ and Mg2+‐Dependent Complex Formation of Tropomyosin with Phosphotroponin (P1TI2C) or Dephosphotroponin (TI2C)
Authors: JAHNKE Ulrike , HEILMEYER Ludwig M. G. 
Published: March 2005

The reduced viscosity of troponin and dephosphotroponin is independent of the protein concentration in both states, either metal‐free or with troponin C saturated with Ca2+ or Mg2+; that of tropomyosin increases linearly as function of the protein concentration, indicating aggregation. Addition of troponin to tropomyosin increases the reduced viscosity over the expected value being maximal at a 1:1 molar ratio of both proteins.The reduced viscosity of a 1:1 molar mixture of phosphotroponin‐Mg4 or dephosphotroponin‐Mg3 increases in two phases as function of the total protein concentration, indicating the formation of two kinds of troponin‐tropomyosin complexes. In the first phase, troponin and tropomyosin form a non‐aggregating 1:1 complex, which is characterized by a value of 0.45 dl/g for the intrinsic viscosity and a sedimentation coefficient of 3.6 S. Employing these two values a molecular weight of 150 000 can be calculated, which is in the range of the sum of molecular weights for troponin and tropomyosin (156 000).In the second phase the troponin‐tropomyosin complex aggregates further, a process described by: n (troponin‐tropomyosin) → (troponin‐tropomyosin)n. This further aggregation occurs upon saturation of the Ca2+‐specific sites in troponin C. A model is discussed which explains the shortening of 1.5 nm per tropomyosin molecule upon the shift of tropomyosin from the periphery into the groove of the actin filament by tropomyosin aggregation.
Metabolism of N8‐Monoacetylspermidine in Rat Hepatoma Cells
Authors: MAMONT Pierre S. , JODER‐OHLENBUSCH Anne‐Marie , SIAT Marlyse 
Published: March 2005

Recent evidence has indicated a role for the acetyl derivatives of polyamines, particularly N8‐monoacetylspermidine, as activators of l‐ornithine decarboxylase in rat hepatoma tissue culture (HTC) cells. This is in contrast with the well‐described negative regulatory control of ornithine decarboxylase exerted by their non‐acetylated counterparts. Because of the possibility of a rapid extracellular and intracellular catabolism of the acetyl derivatives of polyamines, the metabolism of N8‐monoacetylspermidine and its effect on HTC cell ornithine decarboxylase have been investigated, under conditions which eliminate its extracellular catabolism.Differing from previous reports, we demonstrate that N8‐monoacetylspermidine does not elevate ornithine decarboxylase activity when added at low concentrations to the culture medium of HTC cells. Higher concentrations decrease ornithine decarboxylase activity in a dose‐dependent manner. This effect cannot be unambiguously attributed to the effect of the acetyl derivative itself, because of the presence in situ of a very active N8‐monoacetylspermidine deacetylase, which generates spermidine intracellularly.
Kinetic Analysis of the Protonation of a Surface Group of a Macromolecule
Authors: GUTMAN Menachem , NACHLIEL Ester , GERSHON Eli , GINIGER Rina 
Published: March 2005

The dynamics of proton transfer between a surface‐attached acidic moiety and the bulk of the solution was measured using the laser‐induced proton pulse technique. [Gutman, M., Huppert, D. and Pines, E. (1981) J. Am. Chem. Soc. 103, 3709–3713]. The model system for this study consists of pH indicators (either neutral red or bromcresol green) adsorbed on Brij 58 micelles, as defined targets for protonation and a non‐adsorbed proton emitter (2‐naphthol‐3,6‐disulfonate) for generation of protons in bulk. The reaction was measured with 50‐ns time resolution over a time period of about 200 μs. The results were analyzed by a numerical solution of the coupled nonlinear differential equation corresponding with the reaction system. [Gutman, M., et al. (1983) J. Am. Chem. Soc. 105, 2210–2216].Quantitative analysis reveals two independent reactions which govern the observed dynamics: (a) a diffusion‐controlled reaction between the proton and the surface targets; (b) translocation of the protonated target between the hydration layer of the interface and a more hydrophobic one.The contribution of the translocation reaction to the dynamics of surface protonation is more pronounced for compounds like carboxylates or phenolates which increase their hydrophobicity upon protonation. Amines and azoaromatic structures are more hydrophilic in their protonated states, the dynamics of their protonation is less affected by post‐protonation distribution within the microenvironments of the interface.The interrelation between the partial rate constants and the macroscopic time constants and equilibrium parameters is analyzed.
Change in the reactivity of the active‐site serine OH of butyrylcholinesterase caused by a new reversible inhibitor
Authors: GAÁL József , BARTHA Ferenc , BATKE József 
Published: March 2005

The 2‐chloro‐12‐(2‐piperidinoethyl)‐dibenzo[d,g] (1,3,6)‐dioxazocine · HCI (EGYT‐2347), a new specific inhibitor of butyrylcholinesterase inhibits reversibly and non‐competitively the enzymatic hydrolysis of butyrylthiocholine iodide (Ki= 0.15 μM, at 37°C in 0.1 M Tris/HCI, pH 7.5).The theoretical progress curve of product accumulation has been developed for the case when a non‐competitive reversible inhibitor (EGYT‐2347) and an active‐site‐directed irreversible inhibitor (diisopropylfluorophosphate) act simultaneously. By the aid of this approach it was concluded that the butyrylcholinesterase–EGYT‐2347 binary complex does not react with diisopropylfluorophosphate either because of a structural change caused by binding or by the direct steric hindrance of EGYT‐2347.
Glutamyl‐tRNA synthetases from wheat
Authors: RATINAUD Marie Hélène , Thomes Jean Claude , JULIEN Raymond 
Published: March 2005

Three dimeric glutamyl‐tRNA synthetases (GluRS) were isolated from extracts of quiescent wheat germ and wheat chloroplasts.

The chloroplast enzyme (Mr= 110000), called GluRS C, exhibits a prokaryotic (Escherichia coli) tRNA specificity.
Two enzymes were found in the quiescent germ and were separated on phosphocellulose P11: one called GluRS P, probably the mitochondrial enzyme, has the same tRNA specificity as GluRS C; the other, called GluRS E, has eukaryotic (wheat germ) tRNA specificity. Both enzymes exhibit a molecular weight close to 160000.
Each of these enzymes co‐eluate on hydroxyapatite and phosphocellulose chromatographies with an unstable active monomer whose molecular weight is approximately half that of the corresponding dimer. Two assumptions are discussed about these monomers.
Purification, subunit structure and immunological comparison of fructose‐bisphosphate aldolases from spinach and corn leaves
Authors: KRÜGER Ingo , SCHNARRENBERGER Claus 
Published: March 2005

The cytosol and chloroplast fructose‐bisphosphate aldolases from spinach leaves were separated by ion‐exchange chromatography on DEAE‐cellulose, and were purified by subsequent affinity chromatography on phosphocellulose to apparent homogeneity as judged from polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The two aldolases had specific activities of 7.2 and 7.8 units mg protein−1. Molecular weight determinations by electrophoresis in sodium dodecyl sulfate gels and by sedimentation velocity centrifugation in sucrose gradients showed that the aldolases contained four subunits of Mr 38000 and 35000, respectively. Antibodies against the cytosol and chloroplast aldolase from spinach leaves were raised in a guinea pig and in a rabbit, respectively. In the Ouchterlony double‐diffusion test, the two aldolases did not cross‐react. A small degree of cross‐reaction was observed by a test in which immune complexes were adsorbed to a solid‐phase support (Staphylococcus aureus Cowan 1 cells) and nonbound enzyme activity was determined after centrifugation. These results imply major structural differences between the two spinach leaf aldolases.Only one major aldolase could be resolved on DEAE‐cellulose from corn leaves. The aldolase was purified and had a specific activity of 6.4 units · mg protein−1. The corn leaf aldolase cross‐reacted with the antiserum raised against the chloroplast enzyme from spinach leaves, but not with the other antiserum. Thus, the corn leaf aldolase could be identified as a chloroplast enzyme. Since aldolase activity is mostly restricted to the bundle sheath cells of corn leaf, it was concluded that it is compartmentalized in the chloroplasts of these cells but not in chloroplasts of the mesophyll cells.
Association of rabbit muscle glycolytic enzymes with filamentous actin
Authors: WESTRIN Hjalmar , BACKMAN Lars 
Published: March 2005

The association between purified glycolytic enzymes and filamentous actin from rabbit muscle has been studied by counter‐current distribution. The co‐distribution of a glycolytic enzyme and filamentous actin leads to a significant change in the counter‐current distribution profile of the enzyme whereas that of actin is unaffected. The changes in the distribution profiles clearly demonstrated that all glycolytic enzymes studied, though to different extents, bind to filamentous actin.The aqueous two‐phase system used for the studies contained dextran, poly(ethyleneglycol) and 150 millimolal potassium phosphate buffer, pH 7.0. Since the ionic strength of the two‐phase system is determined mainly by the buffer, the glycolytic enzymes are evidently able to associate with filamentous actin, at least in the presence of neutral polymers, at ionic strengths comparable to or higher than those assumed to prevail in vivo.
An evaluation of the role of a pyroglutamyI peptidase, a post‐proline cleaving enzyme and a post‐proline dipeptidyI amino peptidase, each purified from the soluble fraction of guinea‐pig brain, in the degradation of thyroliberin in vitro
Authors: BROWNE Padraig , O'CUINN Gerard 
Published: March 2005

The degradation of thyroliberin (<Glu‐His‐Pro‐NH2) to its component amino acids by the soluble fraction of guinea pig brain is catalysed by four enzymes namely a pyroglutamate aminopeptidase, a post‐proline cleaving enzyme, a post‐proline dipeptidyl aminopeptidase and a proline dipeptidase.1. The pyroglutamate aminopeptidase was purified to over 90% homogeneity with a purification factor of 2868‐fold and a yield of 5.7%. In addition to catalysing the hydrolysis of thyroliberin, acid thyroliberin and pyroglutamate‐7‐amido‐4‐methylcoumarin the pyroglutamate aminopeptidase catalysed the hydrolysis of the peptide bond adjacent to the pyroglutamic acid residue in luliberin, neurotensin, bombesin, bradykinin‐potentiating peptide B, the anorexogenic peptide and the dipeptides pyroglutamyl alanine and pyroglutamyl valine. Pyroglutamyl proline and eledoisin were not hydrolysed.2. The post‐proline cleaving enzyme was purified to apparent electrophoretic homogeneity with a purification factor of 2298‐fold and a yield of 10.6%. The post‐proline cleaving enzyme catalysed the hydrolysis of thyroliberin and N‐benzyloxycarbonyl‐glycylproline‐7‐amido‐4‐methylcoumarin. It did not catalyse the hydrolysis of glycylproline‐7‐amido‐4‐methylcoumarin or His‐Pro‐NH2.3. The post‐proline dipeptidyl aminopeptidase was partially purified with a purification factor of 301‐fold and a yield of 8.9%. The post‐proline dipeptidyl aminopeptidase catalysed the hydrolysis of His‐Pro‐NH2 and glycylproline‐7‐amido‐4‐methylcoumarin but did not exhibit any post‐proline cleaving endopeptidase activity against thyroliberin or N‐benzyloxycarbonyl‐glycylproline‐7‐amido‐4‐methylcoumarin.4. Studies with various functional reagents indicated that the pyroglutamate aminopeptidase could be specifically inhibited by 2‐iodoacetamide (100% inhibition at an inhibitor concentration of 5μM), the post‐proline cleaving enzyme by bacitracin (IC50= 42 μM) and the post‐proline dipeptidyl aminopeptidase by puromycin (IC50= 46 μM). Because of their specific inhibitory effects these three reagents were key elements in the elucidation of the overall pathway for the metabolism of thyroliberin by guinea pig brain tissue enzymes.