bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bordetella pertussis adenylate cyclase
Authors: GENTILE Fabrizio , RAPTIS Anastassios , KNIPLING Leslie G. , WOLFF J. 
Published: March 2005

Exposure of Chinese hamster ovary, mouse adrenal cortex tumor (Y‐1), THP‐1 and U‐937 cells and human erythrocytes to adenylate‐cyclase‐containing urea extracts of Bordetella pertussis (strain 114) organisms promotes the formation of large concentrations of intracellular CAMP. Accumulation is dependent on dose and temperature, with significant accumulation occurring at 4° C, and is virtually instantaneous, with a doubling at 1 min. There is an absolute Ca2+ requirement but external calmodulin (the activator of cyclase activity) has no effect except in erythrocytes and U‐937 cells, where it reduces CAMP accumulation. However, calmodulin antagonists inhibit cAMP accumulation. In Y‐1 adrenal cells the urea‐extract adenylate cyclase stimulates steroidogenesis.Anti‐(B. pertussis) antibodies inhibit cyclase activity and prevent further cAMP accumulation after 10 min in cells previously exposed to urea extract. The same effect is obtained by washing. This suggests that a portion of the cyclase is associated with cells in a form not accessible to antibody or washing but accessible to substrate, which we interpret as internalized enzyme with a short lifetime. Continuing CAMP accumulation thus appears to need a continuing source of external cyclase.Inhibitors of the effect of diphtheria toxin, such as NH4Cl, methylamine, chloroquin or monensin, have no inhibitory effect on the accumulation of intracelluar cAMP promoted by the internalized adenylate cyclase of urea extracts of B. pertussis organisms. We conclude that entry of the cyclase into cells is not by receptor‐mediated endocytosis.
Structural requirements of lipid A species in activation of clotting enzymes from the horseshoe crab, and the human complement cascade
Authors: TAKADA Haruhiko , KOTANI Shozo , TANAKA Shigenori , OGAWA Tomohiko , TAKAHASHI Ichiro , TSUJIMOTO Masachika , KOMURO Tetsuo , SHIBA Tetsuo , KUSUMOTO Shoichi , KUSUNOSE Naoto , HASEGAWA Akira , KISO Makoto 
Published: March 2005

The structure/activity relationship of lipid A, a bioactive center of endotoxic lipopolysaccharides, in the activation of the clotting enzyme cascade of a horseshoe crab amoebocyte lysate (Limulus activity) and the complement system in human serum, was examined using synthetic lipids A and related compounds. Regarding Limulus activity, a newly developed colorimetric method, which utilizes a mixture of recombined clotting factors and a chromogenic substance, was much more sensitive for detecting changes in the chemical structure of test compounds than the conventional gelation method using the amoebocyte whole lysate.(β1‐6)‐d‐Glocosamine disaccharide bisphosphates, which had neither 3‐hydroxyacyl nor 3‐acyloxyacyl groups, and acylglucosamine phosphates, which in structure correspond or are analogous to the non‐reducing or reducing moieties of lipids A and biosynthetic disaccharide lipid A precursors showed only negligible activity in the colorimetric tests, but they exhibited a distinct though much weaker gelation activity than the parent disaccharide molecules. The assay results obtained by the colorimetric Limulus test correlate better with the pyrogenicity of the test synthetic compounds than those given by the gelation method, although the dependence of pyrogenicity on chemical structure is greater. The presence of 3‐hydroxyacyl groups on the bisphosphorylated (β1‐6)‐d‐glucosamine disaccharide backbone is the prerequisite for effective activation of the clotting enzyme cascade of horseshoe crab amoebocyte lysate, while the presence of an adequate number (one or two) of 3‐acyloxyacyl groups on the disaccharide bisphosphate backbone is needed for full pyrogenicity.Complement activation, on the other hand, showed structural requirements quite different from those for the colorimetric Limulus activity and the pyrogenicity. The disaccharide compounds that had only non‐hydroxylated acyl groups, acylated glucosamine phosphates that had the structure of the non‐reducing portion of lipids A and biosynthetic disaccharide precursors, which were scarcely active in the colorimetric Limulus test, caused complement activation comparable to or sometimes stronger than that of the parent disaccharide molecules. Acylglucosamine phosphates, corresponding in structure to the reducing moiety of disaccharide compounds, however, showed little activity.
Displacement of histones by sperm‐specific proteins at different stages of spermatogenesis of squid
Authors: KADURA Sergey N. , KHRAPUNOV Sergey N. 
Published: March 2005

Changes in the composition of the chromatin basic proteins during spermatogenesis of the squid Illex argentinus were studied. The core histones of I. argentinus slightly differ from those of calf thymus in the subfractional composition of histones H2A and H2B.A similar amino acid composition is revealed in the histones H1 of the squid I. argentinus and calf thymus. Histone H1 of the squid has a lower molecular mass and a special subfractional composition as compared to those of calf thymus, grass carp and carp studied formerly [Kadura et al. (1983) Comp. Biochem. Physiol. 743, 343–3501. Neither the fractional nor subfracitonal composition of histones changes during spermatogenesis. The two new proteins were revealed in the chromatin composition of squid testes and spermatozoa illexines I1 and I2. Illexine I2 is composed of two subfractions I2‐1 and I2‐2. Illexine I2 shows a high content of arginine (75 mol/100 mol). Serine (10 mol/100 mol), histidine (3,2 mol/100 mol) and tyrosine residues (2,9 mol/100 mol) are also present. Illexine I1 shows the presence of arginine (45,6 mol/100 mol), lysine (7.6 mol/100 mol), serine (11.4 mol/100 mol), hystidine (2.3 mol/100 mol) and tyrosine residues (2.8 mol/100 mol).Molecular masses of illexines I2 and I1 are approximately 7 kDa and 9 kDa respectively. It is supposed that during spermatogenesis the histones are displaced in two‐stage order: histones → I1→ I2.
Rearrangements of chromatin structure during spermatogenesis of squid
Authors: KHRAPUNOV Sergey N. , KADURA Sergey N. , DRAGAN Anatol I. 
Published: March 2005

A step wise replacement of somatic histones on sperm‐specific proteins (we have termed them illexines I1 and I2) is found to occur during spermatogenesis of squid Illex argentinus [Kadura, S. N. and Khrapunov, S. N. (1988) Eur. J. Biochem. 175, 603–607]. The chromatin from nuclei of squid immature testes has a nucleosomal DN A repeat which corresponds to the nucleosomal repeat of calf thymus chromatin (195 ± 5 bp). As spermatozoa become mature and illexine I2 accumulates in the chromatin, the nucleosomal structure of the latter disappears and chromatin compacting takes place. The chromatin DNA from squid spermatozoa is highly resistant to micrococcal nuclease action.Spectrophotometry and spectrofluorimetry were to establish that neither illexine I1 nor illexine I2 forms a globular structure in solution under any conditions studied. Illexine I2 (approx. 7 kDa) shows a high affinity to DNA and remains bound to it under conditions when complexes of illexine I1 (approx. 9 kDa) and salmine (approx. 4.5 kDa) with DNA completely dissociate. This fact, allowing for a similar content (about 75%) of arginine in illexine I2 and salmine, suggests high clustering of arginine residues in the composition of illexine I2.It is suggested that the initial stage of histone substitution with illexine I1, which has a more moderate affinity to DNA than illexine I2, prepares chromatin for the formation of a highly packed structure by illexine I2 during squid spermatogenesis.
A mathematical model of the Calvin photosynthesis cycle
Authors: PETTERSSON Gosta , RYDE‐PETTERSSON Ulf 
Published: March 2005

A mathematical model is presented for photosynthetic carbohydrate formation in C3 plants under conditions of light and carbon dioxide saturation. The model considers reactions of the Calvin cycle with triose phosphate export and starch production as main output processes, and treats concentrations of NADPH, NAD+, CO2, and H+ as fixed parameters of the system. Using equilibrium approximations for all reaction steps close to equilibrium, steady‐state and transient‐state relationships are derived which may be used for calculation of reaction fluxes and concentrations of the 13 carbohydrate cycle intermediates, glucose 6‐phosphate, glucose 1‐phosphate, ATP, ADP, and inorganic (Ortho)phosphate.
Predictions of the model were examined with the assumption that photosynthate export from the chloroplast occurs to a medium containing orthophosphate as the only exchangeable metabolite. The results indicate that the Calvin cycle may operate in a single dynamically stable steady state when the external concentration of orthophosphate does not exceed 1.9 mM. At higher concentrations of the external metabolite, the reaction system exhibits overload breakdown; the excessive rate of photosynthate export deprives the system of cycle intermediates such that the cycle activity progressively approaches zero.
Reactant concentrations calculated for the stable steady state that may obtain are in satisfactory agreement with those observed experimentally, and the model accounts with surprising accuracy for experimentally observed effects of external orthophosphate on the steady‐state cycle activity and rate of starch production.
Control analyses are reported which show that most of the non‐equilibrium enzymes in the system have a strong regulatory influence on the steady‐state level of all of the cycle intermediates. Substrate concentration control coefficients for cycle enzymes may be positive, such that an increase in activity of an enzyme may raise the steady‐state concentration of the substrate is consumes.
Under optimal external conditions (0.15–0.5 mM orthophosphate), reaction flux in the Calvin cycle is controlled mainly by ATP synthetase and sedoheptulose bisphosphatase; the cycle activity approaches the maximum velocity that can be supported by the latter enzyme. At lower concentrations of external orthophosphate the cycle activity is controlled almost exclusively by the phosphate translocator. At high external orthophosphate concentrations the phosphate translocator resumes predominant control, but also other non‐equilibrium enzymes gain strong flux control with one notable exception: ribulosebisphosphate carboxylase has no significant regulatory influence on the cycle activity under conditions of light and CO2 saturation, nor does it control the concentration of any cycle intermediate other than its substrate.
Microsomal and cytosolic epoxide hydrolases, the peroxisomal fatty acid β‐oxidation system and catalase
Authors: STEINBERG Pablo , SCHLADT Ludwig , DIENES Hans Peter , TIMMS Christopher , OESCH Franz 
Published: March 2005

A number of structurally unrelated hypolipidaemic agents and certain phthalate‐ester plasticizers induce hepatomegaly and proliferation of peroxisomes in rodent liver, but there is relatively limited data regarding the specific effects of these drugs on liver non‐parenchymal cells. In the present study, liver parenchymal, Kupffer and endothelial cells from untreated and fenofibrate‐fed rats were isolated and the activities of two enzymes associated with peroxisomes (catalase and the peroxisomal fatty acid P‐oxidation system) as well as cytosolic and microsomal epoxide hydrolase were measured.Microsomal epoxide hydrolase, cytosoic epoxide hydrolase and catalase activities were 7 – 12‐fold higher in parenchymal cells than in Kupffer or endothelial cells from untreated rats; the peroxisomal fatty acid β‐oxidation activity was only detected in parenchymal cells. Fenofibrate increased catalase, cytosolic epoxide hydrolase and peroxisomal fatty acid β‐oxidation activities in parenchymal cells by about 1.5, 3.5‐ and 20‐fold, respectively. The induction of catalase (2 ‐ 3‐fold) and cytosolic epoxide hydrolase (3 ‐ 5‐fold) was also observed in Kupffer and endothelial cells; furthermore, a low peroxisomal fatty acid β‐oxidation activity was detected in endothelial cells. Morphological examination by electron microscopy showed that peroxisomes were confined to liver parenchymal cells in untreated animals, but could also be observed in endothelial cells after administration of fenofibrate.
Chorismate mutase:prephcnate dehydratase from Acinetobacter calcoaceticus
Authors: AHMAD Suhail , WILSON Anna‐Tan , JENSEN Roy A. 
Published: March 2005

The bifunctional P protein (chorismate mutase: prephenate dehydratase) from Acinetobacter calcoaceticus has been purified. It was homogeneous in polyacrylamide gels and was more than 95% pure on the basis of the immunostaining of purified P protein with the antibodies raised against the P protein. The native enzyme is a homodimer (Mr = 91000) composed of 45‐kDa subunits. A twofold increase in the native molecular mass of the P protein occurred in the presence of L‐phenylalanine (inhibitor of both activities) or L‐tyrosine (activator of the dehydratase activity) during gel filtration.Chorismate mutase activity followed Michaelis‐Menten kinetics with a Km of 0.55 mM for chorismate. L‐Phenylalanine was a relatively poor non‐competitive inhibitor of the mutase activity. The chorismate mutase activity was also competitively inhibited by prephenate (reaction product). Substrate‐saturation curves for the dehydratase activity were sigmoidal showing positive cooperativity among the prephenate‐binding sites. L‐Tyrosine activated prephenate dehydratase strongly but did not abolish positive cooperativity with respect to prephenate. L‐Phenylalanine inhibited the dehydratase activity, and the substrate‐saturation curves became increasingly sigmoidal as phenylalanine concentrations were increased with happ values changing from 2.0 (no phenylalanine) to 4.0 (0.08 mM L‐phenylalanine). A sigmoidal inhibition curve of the dehydratase activity by L‐phenylalanine gave Hill plots having a slope of ‐ 2.9. Higher ionic strength increased the dehydratase activity by reducing the positive cooperative binding of prephenate, and the sigmoidal substrate‐saturation curves were changed to near‐hyperbolic form. The happ values decreased with increase in ionic strength.Antibodies raised against the purified P protein showed cross‐reactivity with the P proteins from near phylogenetic relatives of A. calcoaceticus. At a greater phylogenetic distance, cross‐reaction was superior with P protein from Neisseria gonorrhaeae than with that from the more closely related Escherichia coli.
Monomerization of cytochrome oxidase may be essential for the removal of subunit III
Authors: FINEL Moshe , WIKSTRÖM Mårten 
Published: March 2005

Incubation of cytochrome oxidase, under conditionsused as intial steps in treatment to remove sub‐unit III, causes at least partial monomerization of the enzyme.
The extent of removal of subunit III by anion‐exchange fast protein liquid chromatography (FPLC) is much increased if the enzyme is fully monomerized before it is applied to the column.
Subunit III is incompletely removed by chymotrypsin treatment. A digestion product of subunit III migrating in SDS‐PAGE like subunit IV, is detected with specific antibodies. The amount of this product is reduced when monomerization is increased by raising the detergent/protein ration.
The results suggest that monomerization facilities removal of subunit III and exposes it to further chymotrypsin digestion. We propose that subunit III is at least in part located in the junction between the monoments in the cytochrome oxidase dimer.
Forskolin alters sensitivity of the cAMP‐generating system to stimulatory as well as to inhibitory agonists
Authors: MOKHTARI Abdel Rhani , DO KHAC Lien , HARBON Simone 
Published: March 2005

In both the intact guinea pig myometrium and human platelets, cAMP accumulation was enhanced by prostagladin I2 (prostacyclin, PGI2) and forskolin caused rises in platelet cAMP concentration though a single low‐affinity ineraction (Kapp= 90 μ) while in myometrium, activation involved both a low‐affinity (Kapp= 10 μ) and a high‐affinity (Kapp= 0.8 μM) component. The contribution of the high‐affinity component could be reduced when endogenous PGI2 was decreased. In both tissuse, the synergistic effect of forkolin in the presence of PGI2 was mediated by a single high‐affinity ineraction (Kapp= 0.3μM). The data were consistent with a low‐affinity interaction of the diterpene with the cyclase catalytic unit C generation C… forskolin state and with a hogh‐affinity interaction of the diterpene with the activated complex (stimulatory regulatory protein) and C generation the potentiated Gs‐C… forskolin state.
Bothe norepinephrine in platelets and carbachol in the myometrium)via Gi, the inhibitory regulatory protein)inhibited PGI2‐mediated cAMP accumulation (EC50= 100 nM and 8 nM respectively). The persistently activated cAMP‐generation system induced by choleratoxin in the myometrium was also suceptible to inhibition but the EC50 for carbachol was increased to 50 nM and the extent of inhibition was decreased. Forskolin‐mediated effect in platelets was inhibited by norepinephrine aswas the PGI2 response. By contrast, the synergistic state of the cyclase resisted the inhibitory action of norepirne and carbachol in platelets and myometrium repectively. In the myometrium, where the cAMP response due to forskolin alone partially involved some synergistic Gs‐C… forskolin species, carbachol at 50 μM elicited no more than 30% inhibition. Inhibition was partly improved (60% inhibition at 1 μM carbachol)when the contribution of the Gs‐C species was decreased by lowering the concertration of lacal PGI2. Partial inhibition by norepinephrine was similarly observed in platelets under partial synergistic condition. The data suggest that recepto‐mediated inhibition of cAMP generation could be differentially expressed depending on the nature of the active species of the cyclase involved in the stimulatory responses.
Murine hybridoma/plasmacytoma growth factor
Authors: SIMPSON Richar J. , MORITZ Robert L. , RUBIRA Michael R. , VAN SNICK Jacques 
Published: March 2005

Murine interleukin‐HP1 (HP1) was originally identified as a T‐cell derived lymphokine with growth factor activity for B‐cell hybridomas and plasmacytomas. This growth factor was recently shown to stimulate both normal B‐cell differentiation and T‐cell growth factor activity. We have determined the complete amino acid sequence of HP1 on 40 μg (approximately 2 nmol) protein using a combination of sensitive microbore column (1.0 and 2.1 mm internaldiameter) HPLC, peptide mapping and automated amino acid microsequence analysis. Ion‐pairing chromatography was employed to isolate hydrophilic peptides which were not retained on conventional reversed‐phase HPLC systems. The molecule consists of 187 amino acid residues with a calculated molecular mass of 21710 Da.Although there is virtually no similarity between the NH2‐terminal region of HP1 and its human biological counterpart (26‐kDa protein/interferon‐β2= B‐cell stimulatory factor‐2/interleukin‐6), these studies demonstrate extensive amino acid similarity inthe middle and COOH‐teminal regions of these molecules suggesting that HP1 is the murine homologue of human interleukin‐6.
Structural and immunochemical studies of the lipopolysaccharide from a new provisional serotype of Shigella flexneri
Authors: WEHLER Thomas , CARLIN Nils I. A. 
Published: March 2005

The chemical structure of the O‐antigen of a proposed new provisional serotype of Shigella flexneri has been determined. Methylation analysis, GLC‐MS, 1H‐NMR and 13C‐NMR showed that the linear O‐antigenic polysaccharide is the same as for all S. flexneri [Kenne, L., Lindberg, B., Petersson, K. & Romanowska, E. (1977) Carbohydr. Res. 56, 363‐370]. A novel structural feature is that the disaccharide α‐D‐Glcp‐(1→2)‐α‐D‐Glcp is linked to O4 of the N‐acetyl‐glucosamine residue.

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Western blotting of the lipopolysaccharide with an E. coli R3 core‐specific monoclonal antibody, suggested the presence of anE. coli R3 core.
The poly(A)‐binding protein facilitates in vitro translation of poly(A)‐rich mRNA
Authors: GROSSI de SA Maria‐Fatima , STANDART Nancy , MARTINS de SA Cezar , AKHAYAT Omar , HUESCA Michèle , SCHERRER Klaus 
Published: March 2005

To investigate the role of the 73‐kDa poly(A)‐binding protein in protein synthesis, the effect of the addition of homo‐polyribonucleotides on the translation of polyadenylated and non‐adenylated mRNA was studied in the rabbit reticulocyte lysate. Poly(A) was found to be the most effective polynucleotide in inhibiting duck‐globin mRNA translation, whereas it had no effect on the translation of polyribosomal duck‐globin mRNP, or on the endogenous synthesis of the rabbit reticulocyte lysate. The translation of poly(A)‐free mRNA was not affected by the addition of poly(A).Furthermore, we found that the inhibiting effect of poly(A) can be reversed by addition of purified poly(A)‐binding protein. It is thus likely that the 73‐kDa poly(A)‐binding protein is an essential factor necessary for poly(A)‐rich mRNA translation.
Multiplicity of interactions between dromedary hemoglobin and solvent components
Authors: BERTOLLINI Alberto , SANTUCCI Roberto , AMICONI Gino , ASCOLI Franca , CURRELL Douglas L. , MURSAL Omar , BRUNORI Maurizio 
Published: March 2005

The interaction of dromedary hemoglobin with various solvent components [2‐(p‐chlorophenoxy)‐2‐methylpropionic acid (CFA), 2,3‐bisphospho‐D‐glycerate (glycerate‐2,3‐P2) and chloride] has been studied.

CFA greatly lowers the oxygen affinity of dromedary hemoglobin.
The oxygen‐linked CFA binding sites are probably located in the deoxy derivative at the α cleft, while in the oxy form and in the presence of two other effectors (glycerate‐2,3‐P2 and chloride) additional, structurally and possibly functionally relevant binding site(s) should be considered.
Both CFA and glycerate‐2,3‐P2 stabilize the deoxy‐like tertiary structure in the oxy derivative.
Chloride appears to be fundamental to obtain quaternary structural changes.
Interaction energy, retained in the protein when the three ligands (CFA, glycerate‐2,3‐P2 and chloride) are bound to the oxy form, favours intermediates not stable if only one or two allosteric effector(s) is (are) present on the protein.
The oxygen affinity appears to be related to both tertiary and quaternary structural changes, while cooperativity is largely invariant with solvent conditions.

In conclusion, the functional properties of dromedary hemoglobin do not depend in any simple way on the variety of stabilized conformations.