bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Complete Amino‐Acid Sequence of Histone H2B(2) from Sperm of the Sea Urchin Parechinus angulosus
Authors: STRICKLAND Walter N. , STRICKLAND Marie , BRANDT Wolf F. , VON HOLT Claus 
Published: March 2005

Sperm histone H2B(2)Parechinus consists of a single polypeptide chain of the following 143 amino acids: Pro‐Arg‐Ser‐Pro‐Ala‐Lys‐Thr‐Ser‐Pro‐Arg‐Lys‐Gly‐Ser‐Pro‐Arg‐Lys‐Gly‐Ser‐Pro‐Ser‐Arg‐Lys‐Ala‐Ser‐Pro‐Lys‐Arg‐Gly‐Gly‐Lys‐Gly‐Ala‐Lys‐Arg‐Ala‐Gly‐Lys‐Gly‐Gly‐Arg‐Arg‐Arg‐Arg‐Val‐Val‐Lys‐Arg‐Arg‐Arg‐Arg‐Arg‐Arg‐Glu‐Ser‐Tyr‐Gly‐Ile‐Tyr‐Ile‐Tyr‐Lys‐Val‐Leu‐Lys‐Gln‐Val‐His‐Pro‐Asp‐Thr‐Gly‐Ile‐Ser‐Ser‐Arg‐Ala‐Met‐Ser‐Val‐Met‐Asn‐Ser‐Phe‐Val‐Asn‐Asp‐Val‐Phe‐Glu‐Arg‐Ile‐Ala‐Gly‐Glu‐Ala‐Ser‐Arg‐Leu‐Thr‐Ser‐Ala‐Asn‐Arg‐Arg‐Ser‐Thr‐Val‐Ser‐Ser‐Arg‐Glu‐Ile‐Gln‐Thr‐Ala‐Val‐Arg‐Leu‐Leu‐Leu‐Pro‐Gly‐Glu‐Leu‐Ala‐Lys‐His‐Ala‐Val‐Ser‐Glu‐Gly‐Thr‐Lys‐Ala‐Val‐Thr‐Lys‐Tyr‐Thr‐Thr‐Ser‐Arg. In a previously published partial sequence positions 25, 34, 40 and 41 were incorrectly assigned.The amino‐terminal one third of sperm histone H2B(2)Parechinus is highly basic containing a repeating pentapeptide occurring over the first 24 residues. This repeating pentapeptide is different to that of sperm histone H2B(1)Parechinus. In this region there is very little amino acid sequence homology between H2B(1)Parechinus, H2B(2)Parechinus on the one side and H2Bcalf thymus on the other side, but all three proteins are highly basic in their N‐terminal parts.The carboxyl‐terminal two thirds of sperm histone H2B(2) is hydrophobic except for a short polar region of 20 amino acids. The carboxyl‐terminal region shows a very high amino acid sequence homology between the three H2B histones. Much of the variability occurs in the short polar region whereas the hydrophobic regions are almost completely constant. The majority of the amino acid substitutions that occur in the carboxyl end are conservative.The three H2B protein sequences are compared and the functional and evolutionary significance of the changes is discussed.
Characterization of the Protein Moiety of Messenger Ribonucleoprotein Complexes from Duck Reticulocytes by Two‐Dimensional Polyacrylamide Gel Electrophoresis
Authors: MUELLER Rita U. , CHOW Virginia , GANDER Eugen S. 
Published: March 2005

The protein moiety of duck globin messenger ribonucleoprotein complexes isolated by oligo(dT)‐cellulose chromatography or by sucrose gradient centrifugation was analysed by two‐dimensional polyacrylamide gel electrophoresis under conditions where the separation in the first dimension occurs according to charge and in the second according to molecular weight.By comparing the pattern of protein from the mRNA · protein complex with that of ribosomal subunits we found that two acidic proteins with an identical molecular weight of about 49000 and three basic proteins of about Mr 56000, 64000 and 73000 were associated with the duck globin mRNA but were absent from either puromycin/high‐salt‐derived or ‘run‐off’ ribosomal subunits.The comparison of the proteins from the complex with mRNA with those found in the 0.5 M KCl wash, commonly used as the source of initiation factors, showed also that only the 49000‐Mr protein from the complex could possibly be present in the 0.5 M KCl wash of polyribosomes; proteins with mobilities similar to the other three proteins complexed with mRNA were not detected in the salt wash of polyribosomes.
The Disialosyl Group of Glycoproteins
Authors: FINNE Jukka , KRUSIUS Tom , RAUVALA Heikki , HEMMINKI Kari 
Published: March 2005

A sensitive method for the determination of disialosyl (α‐N‐acetylneuraminyl‐(2‐8)‐N‐acetyl‐neuraminyl) groups was developed. The method is based on the quantitation of the amount of 8‐O‐substituted neuraminic acid by methylation analysis using mass fragmentographic detection with two different m/e values. Lability of the 8‐O‐substituent of neuraminic acid to neuraminidase is taken as an indication for the presence of a disialosyl sequence.Considerable differences in the amount of disialosyl groups were observed between glycopeptides from different tissues of the rat. The proportion of 8‐O‐substituted neuraminic acid as compared to total glycopeptide‐bound neuraminic acid was 8.5% in brain, 3.1% in liver, 2.6% in diaphragmatic muscle and 3.0% in small intestinal mucosa, whereas glycopeptides derived from kidney, gastric mucosa, erythrocytes and plasma did not contain disialosyl groups.The disialosyl groups were enriched in glycoproteins of the membranous fractions of liver and brain, whereas only small amounts were observed in the soluble fractions. The proportion of glycopeptide‐bound 8‐O‐substituted neuraminic acid in the brain of young rats (13.9%) was higher than in the brain of adult animals. The highest proportion of 8‐O‐substituted neuraminic acid (19.8%) was observed in glycopeptides of the plasma membrane fraction of the young rat brain.
Studies on Hemoglobin Tryptophany1 Contact Residues in the Haptoglobin · Hemoglobin Complex
Authors: ROGARD Monique , WAKS Marcel 
Published: March 2005

Hemoglobin and apohemoglobin bind haptoglobin in the same molar ratio. Structural studies on haptoglobin · hemoglobin complex do not suggest any important structural changes in either protein upon binding. However, when apohemoglobin is bound to haptoglobin, a marked reduction in secondary structure, attributed to unfolding of globin chains, has been observed.Here we describe some properties of the haptoglobin · apohemoglobin (Hp · apoHb) complex, prepared by isoelectric focusing in the presence of an excess of haptoglobin. This complex does not exhibit the irreversibility of complexes obtained with hemoglobin in identical experimental conditions.The ‘freezing’ of the conformation of apohemoglobin upon binding to haptoglobin has been studied by fluorescence quenching experiments carried out in the presence of 8 M acrylamide. Changes in conformation of haptoglobin upon binding to apohemoglobin have been detected by titration of the exposed tryptophans using N‐bromosuccinimide.Comparison of the additivity of exposed tryptophans in the complexes reveal that two tryptophans become inaccessible in the complex formation of haptoglobin with hemoglobin but not with apohemoglobin. These tryptophans, probably located on the α1β2 contact interface of hemoglobin, have been tentatively identified as Trp‐C3(37)β.
α‐Galactosidase from Saccharomyces carlsbergensis
Authors: LAZO Pedro S. , OCHOA Amparo G. , GASCÓN Santiago 
Published: March 2005

1. The α‐galactosidase of Saccharomyces carlsbergensis is an inducible enzyme which is localized mainly outside the cell membrane and which is secreted into the culture medium in increasing amounts during the growth cycle.2. The soluble form of α‐galactosidase localized inside the cell appears to have the same characteristics as the external one, contrasting with the different forms found in the case of invertase. Although some activity is membrane‐bound, this activity, when solubilized with detergent, has the same characteristics as the external form of the enzyme.3. A procedure has been developed by which the enzyme has been purified using batch adsorption with DEAE‐Sephadex and column chromatography in DEAE‐Sephadex, DEAE‐cellulose and Sephadex G‐200, using the supernatant of a culture of Saccharomyces carlsbergensis grown in yeast nitrogen base complemented with galactose.4. The purified enzyme, which is homogeneous by chromatographic criteria and polyacrylamide gel electrophoresis, appears to be glycoprotein.5. Invertase copurifies with the α‐galactosidase but because of its lower stability, together with the fact that the synthesis of both enzymes can be controlled separately, it was possible to obtain preparations in which the contaminant activity was approximately 1%.
Drug Oxidations Dependent on Cytochrome P‐450 in Isolated Hepatocytes
Authors: WEIGL Klaus , SIES Helmut 
Published: March 2005

1. Isolated hepatocytes from male rats pretreated with phenobarbital were used to study metabolic effects associated with monooxygenase activity dependent on cytochrome P‐450. The hepatocytes metabolized an added drug substrate, [dimethylamino‐14C]aminopyrine (1 mM) at an N‐demethylation rate of 1.31 ± 0.1 μmol × min−1× g (dry weight of hepatocytes)−1. The overall ATP/ADP ratios were 5.0 in the presence of aminopyrine, similar to the controls.2. The levels of citrate and isocitrate decreased, and the citrate/2‐oxoglutarate ratio decreased to 55% of the control in the presence of drug substrates (aminopyrine, ethylmorphine, hexobarbital), correlating well with the decrease in the overall NADPH/NADP+ ratio observed earlier with the perfused liver. It is concluded that supply of NADPH by extramitochondrial isocitrate dehydrogenase accompanies the NADPH supply by the pentosephosphate cycle, so that in spite of the larger capacity of the latter a portion of the reducing equivalents is derived from the mitochondria via the tricarboxylates even in the fed state. This results from the necessity of relieving the inhibition of glucose‐6‐phosphate dehydrogenase by NADPH for activation of the pentosephosphate cycle.3. Subfractionation of hepatocytes from fed rats with the digitonin method revealed decreases of the citrate/2‐oxoglutarate ratios both in the particulate (mitochondrial) and the supernatant (cytosolic) fractions, corresponding to a positive shift in the NADPH redox potential of about 10 mV (or to a decrease of the free [NADPH]/[NADP+] ratio to one‐half) in both compartments as calculated from the combined equilibria of NADP+‐linked isocitrate dehydrogenase and aconitate hydratase.4. Only in cells from fasted, not from fed rats, the rate of aminopyrine N‐demethylation was diminished to 2/3 in the presence of aminotransferase inhibitors, suggesting a requirement for transamination steps in the transfer of NADPH‐reducing equivalents from mitochondria to cytosol under these conditions.
Ca2+ Requirement in ATP‐Induced Activation of Uncoupled Oxidation of Succinate in Isolated Rat‐Liver Mitochondria
Authors: EZAWA I. , OGATA E. 
Published: March 2005

1. Small amounts of Ca2+ cause an ATP‐dependent activation of state 3 oxidation of succinate in rat liver mitochondria in vitro.2. The Ca2+‐induced, ATP‐requiring activation of uncoupled oxidation of succinate (the Ca2+ effect) is blocked by ruthenium red, tetracaine, or high concentrations of K+. It is not blocked by La3+ or Pr3+.3. The Ca2+ effect is demonstrable in mitochondria treated with hyposmotic shock (mitochondria devoid of the outer membrane), freezing‐and‐thawing or aging. Treatment with detergents (sodium deoxycholate and Triton X) causes a loss of the Ca2+ sensitivity.4. For Ca2+ to produce the effect a much longer latent period (several minutes at room temperature) is needed than for ATP or succinate.5. The Ca2+ effect is ATP dose‐related and maximum response is obtained with 0.2 mM ATP.6. The Ca2+ effect is observed in the absence of mitochondrial accumulation of Ca2+ and is Ca2+ dose‐related with external Ca2+ between 0.5 and 50 μM. The half‐maximum response is obtained at about 1 μM.7. The Ca2+ effect is not accompanied by an increase in the penetration of succinate across the mitochondrial membrane as judged from the swelling experiment of Chappell and Crofts, but is accompanied by the activation of succinate dehydrogenase.8. The Ca2+ effect is demonstrable not only in the presence of external oxaloacetate or malonate, but also in conditions where endogenous oxaloacetate accumulation is prevented by the addition of rotenone and glutamate.9. From the above results, a model is proposed in which cytosol Ca2+ alters mitochondrial metabolism by activating succinate dehydrogenase through a change of membrane conformation produced by the Ca2+ interaction with low affinity Ca2+‐binding sites on the outer surface of the inner mitochondrial membrane.
Interaction of the Phosphatidylcholine Exchange Protein with Phospholipids
Authors: WIRTZ Karel W. A. , MOONEN Peter 
Published: March 2005

The phosphatidylcholine exchange protein from bovine liver has a fluorescence emission maximum at 327 nm. Fluorescence was enhanced in the presence of vesicles containing phosphatidylcholine and various amounts of either phosphatidic acid or phosphatidylglycerol. From the increase in fluorescence it was derived that the apparent dissociation constant of the exchange protein‐vesicle complex decreased with an increased vesicle content of acidic phospholipids.Fluorescence indicated that the exchange protein interacted with lysophosphatidylcholine micelles at pH 3.5, 5.9 and 8.5. The increase in fluorescence was most prominent at the acidic pH. Circular dichroism indicated that the α‐helix content of the native protein was low between pH 3.6 and 8.0. Interaction with lysophosphatidylcholine micelles had a negligible effect on the secondary structure of the protein, except at pH 3.6 where distinct minima at 208 nm and 220 nm in the circular dichroic spectrum became apparent.
Pyrimidine Nucleosides in Solution
Authors: FOLLMANN Hartmut , PFEIL Reinhard , WITZEL Herbert 
Published: March 2005

Proton magnetic resonance (PMR) spectra of 45 nucleoside and nucleotide derivatives of uracil, thymine, cytosine, 5‐methylcytosine, and other substituted pyrimidines in water or dimethyl sulfoxide solutions have been analysed in order to correlate structure variations with molecular conformations and to gain insight into the nature of intramolecular forces which are responsible for the ‘rigidity’ of the molecules. Irrespective of the structure of pyrimidine base and the absolute chemical shift values (δ) the C(6)‐H and, to a lesser degree, the C(5)‐H and C(5)‐CH3 resonances are shifted downfield by very similar amounts (Δδ) in the regular nucleosides or in the presence of charged or polar C‐4′ substituents. In detail, the following conformation‐determining effects are seen.1. Ribose vs 2‐deoxyribose substitution of a pyrimidine makes little difference for the chemical environment of base hydrogens but an intact pentofuranose ring (4′‐O) and the exocyclic 5′‐OH group are essential for a nucleoside to assume a specific conformation.2. Profound shielding or deshielding of H‐6 by exocyclic nitrate, halogen, hydroxyl, phosphate, and carboxylate substituents indicates preference for the anti and gauche, gauche conformation ranges in all compounds except in the case of C‐6 substitution.3. Halogen atoms and the hydroxyl group (Δδ∼ 0.30–0.40 ppm) interact with pyrimidine bases by induced polarisation of the C(5)=C(6) double bond, phosphate anions (Δδ∼ 0.50 ppm) interact by the electrostatic attraction mechanism previously described, and in nucleoside 5′‐carboxylates (Δδ > 0.90 ppm) a hydrogen bond between −COO− and H‐6 is formed.4. The deshielding effects caused by a 5′‐OH group and monoanionic 5′‐phosphate are similar (Δδ∼ 0.35–0.45 ppm), supporting the view that intramolecular rigidity of nucleosides and the nucleotide unit is not fundamentally different.This systematic survey, together with our previous studies of adenosine derivatives, provides a rationale for why the majority of both pyrimidine and purine nucleosides and nucleotides in solution exhibit closely comparable conformations, which in turn explain the group specificity of certain key enzymes in nucleic acid metabolism.
Temperature‐Induced Metabolic Alterations in a Thermophilic Bacillus
Authors: REIZER Jonathan , EPSTEIN Israel , GROSSOWICZ Nathan 
Published: March 2005

The effect of growth temperature on activity and rate of synthesis of the α‐aminoisobutyric acid transport system and of several enzymes of Bacillus stearothermophilus var. non diastaticus was investigated. The uptake of α‐aminoisobutyrate, as well as the activities of alanine dehydrogenase and aliphatic amidase were found to be considerably reduced in cultures grown at the near maximal temperature for growth (65°C) as compared to those grown at the optimal temperature for growth (58°C), although the growth rates at both temperatures were similar. The reduced rate at 65°C was due to a decreased differential rate of synthesis of these activities, while the increase in the activities at 58°C was due to de novo synthesis of the enzymes and the α‐aminoisobutyrate transport system rather than to activation of pre‐existing inactive enzymes or permeases. The highest rate of synthesis of alanine dehydrogenase and of the α‐aminoisobutyrate‐uptake system was obtained in cells grown at the near minimal temperature for growth (42–45°C).The reduced rate of enzyme synthesis at the higher temperatures seemed to be due both to an increase in catabolite repression and to faulty oxidative metabolism during growth at these temperatures. The effects mentioned were only partly abolished in a mutant resistant to catabolite repression, when grown at the high temperatures. The thermoadaptation process is discussed in terms of energy production and ATP availability for protein biosynthesis.The alterations of the metabolic activities induced by the environmental temperature were reversible and represent a physiological thermoadaptative response of the cells.
Ionization Dependence of Camphor Binding and Spin Conversion of the Complex between Cytochrome P‐450 and Camphor
Authors: LANGE Reinhard , HUI BON HOA Gaston , DEBEY Pascale , GUNSALUS Irwin. C. 
Published: March 2005

The kinetic rate constants of formation and dissociation of the cytochrome‐P‐450 · camphor complex (Fe3+· RH) have been obtained by low‐temperature (+ 5°C to −20 °C) stopped‐flow experiments. Similarly the high‐spin/low‐spin equilibrium of this complex has been studied as a function of temperature and protonic activity.Both the camphor‐binding mechanism and the high‐spin/low‐spin thermodynamic parameters of Fe3+· RH depend on the protonic activity of the medium in the physiological pH range. The binding rate constants are shown to depend on the ionization of a resdue of the protein, probably a histidine. Linear enthalpy–entropy compensation is observed for the camphor binding as well as for the spin‐state transition. A camphor‐binding‐induced change of the electrostatic potential is discussed.
Sites of Histone/Histone Interaction in the H3 · H4 Complex
Authors: BÖHM Lothar , HAYASHI Hiroaki , CARY Peter D. , MOSS Tom , CRANE‐ROBINSON Colyn , BRADBURY E. Morton 
Published: March 2005

Sites of interaction between histones H3 and H4 have been probed by investigating complex formation, firstly between histone H4 and three peptides cleaved by chemical means from histone H3 (residues 1–90 and 1–120 using cyanogen bromide and residues 42–135 using N‐bromosuccinimide), secondly between histone H3 and two peptides cleaved from histone H4 (residues 1–84 using cyanogen bromide and residues 38–102 using chymotrypsin) and thirdly between the H4 peptide (residues 38–102) and the three H3 peptides (residues 1–90, 1–120 and 42–135).The criterion for complex formation is the appearance of characteristic perturbed resonances in the aromatic region of the 270–MHz proton resonance spectrum of the peptide mixture. It is concluded that loss of 37 N‐terminal residues from histone H4 and 41 N‐terminal residues from histone H3 does not prevent complex formation, whilst the loss of 18 C‐terminal residues from H4 and 45 C‐terminal residues from H3 does prevent it; the last 15 C‐terminal residues of H3 are, however, not required for forming a complex. The regions important for complex formation are therefore defined as residues 42–120 in histone H3 and residues 38–102 in histone H4.
Phosphorylation of the Calcium‐Transport Adenosine Triphosphatase of Cardiac Sarcoplasmic Reticulum by Orthophosphate
Authors: WINKLER Franz , SUKO Josef 
Published: March 2005

Membranes of sacroplasmic reticulum prepared from dog hearts are phosphorylated by [32P]‐orthophosphate in the presence of a calcium load and magnesium. The [32P]phosphate incorporation into sarcoplasmic reticulum follows Michaelis‐Menten kinetics with an apparent Michaelis Constant of 0.5 mM for orthophosphate (pH 7.0). The phosphorylation is pH‐dependent, with an optimum pH of 6.0–6.2 (maximum phosphoprotein steady state level 0.6–0.8 nmol/mg protein).The phosphorylation of sarcoplasmic reticulum by [32P]orthophosphate is strongly inhibited by calcium in the medium. Half‐maximum inhibition occurs at an ionized calcium concentration of about 0.8 μM. The phosphoprotein steady‐state level is reduced by 85–90% by phospholipase‐A treatment or solubilization of calcium‐preloaded sarcoplasmic reticulum with Triton X‐100.The phosphoprotein of sarcoplasmic reticulum formed from [32P]orthophosphate is dephosphorylated by ADP with resultant in ATP synthesis. Phosphoprotein formation and ATP synthesis by sarcoplasmic reticulum are unaltered by azide, dinitrophenol, dicyclohexyl carbodiimide and oligomycin.The phosphoprotein is acid‐stable. The trichloroacetic‐acid‐denaturated 32P‐labelled membrane complex is dephosphorylated by hydroxylamine, indicating that the phosphorylated protein is an acylphosphate.Polyacrylamide gel electrophoresis (performed with phenol/acetic acid/water) of sarcoplasmic reticulum phosphorylated by [32P]orthophosphate demonstrates that the phosphate incorporation occurs into a protein with a molecular weight of about 100 000, as in the case of phosphoprotein formation from ATP.The data suggest that the phosphoprotein of the calcium‐dependent ATPase formed from inorganic phosphate represents a high‐energy intermediate of the reverse reaction of the calcium pump of cardiac sarcoplasmic reticulum.
Regulation of Nitrogen Fixation by Fe‐S Protein II in Azotobacter vinelandii
Authors: SCHERINGS Gerard , HAAKER Huub , VEEGER Cees 
Published: March 2005

1. Several low‐potential electron carriers from different sources can be photoreduced by the system 3,10‐dimethyl‐5‐deazaisoalloxazine/N‐tris(hydroxymethyl)methylglycine. The carriers studied were flavodoxin, ferredoxin I and iron‐sulfur protein II from Azotobacter vinelandii and the flavodoxins from Desulfovibrio vulgaris and Peptostreptococcus elsdenii.2. Electron transport to A. vinelandii nitrogenase was studied, employing different preparations of the enzyme: a crude complex; a complex reconstituted from the 0.27 M and 0.38 M NaCl fractions after DEAE‐cellulose chromatography; a complex reconstituted from the 0.27 M and 0.38 M NaCl fraction plus iron‐sulfur protein II purified from the 0.15 M NaCl fraction. Of all photoreduced carriers tested, only flavodoxin hydroquinone from A. vinelandii catalyzes significant electron transport to these complexes.3. The time course of oxidation of substrate‐amounts of A. vinelandii flavodoxin hydroquinone by catalytic amounts of crude nitrogenase complex shows three characteristic phases: an initial lag phase (1), a phase with constant rate over a range of redox potentials (2) and a final phase with rapidly declining rate (3). It was shown that the Fe‐S protein II is responsible for the lag phase; the potential where phase 2 changes into phase 3 is at a higher value in the presence of Fe‐S protein II. Pre‐reduction of the enzyme photochemically abolishes phase 1 and causes phase 2 to proceed at a higher rate. The rate in phase 2 can be enhanced also by lowering the ‘starting potential’ of the flavodoxin hydroquinone/semiquinone couple.4. A. vinelandii flavodoxin shuttles between its hydroquinone and semiquinone forms during steady‐state electron transfer. Over 90% of the reducing equivalents is recovered in ethylene formed from acetylene. The concentrations of flavodoxin hydroquinone to give half‐maximum rate in the acetylene reduction assay is 3–6 μM. A scheme is proposed for the regulation of electron donation to nitrogenase.