bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human complement factor H
Authors: SCHWAEBLE Wilhelm , SCHWAIGER Helga , BROOIMANS Ricardo A. , BARBIERI Antonia , MÖST Johannes , HIRSCH‐KAUFFMANN Monica , TIEFENTHALER Martin , LAPPIN David F. , DAHA Mohamed R. , WHALEY Keith , DIERICH Manfred P. 
Published: March 2005

Using cDNA clones H‐19 and H‐46, we have shown previously that three different mRNA species (4.3 kb, 1.8 kb and 1.4 kb) for complement factor H are expressed constitutively in human liver. Here we report data suggesting that the expression of these different factor‐H mRNA species is regulated by tissue‐specific control mechanisms.Total RNA and poly(A)‐enriched RNA from various human tissues (heart, lung, temporal cortex, kidney, spleen, bone marrow and muscle) various cell lines (HepG2, HepG3, HepG4, Hep3B, H‐4, Jurkat, Molt4, H‐9, KHos24Os, A‐431, U937, Mono Mac 6 and Raji) and from primary cultures of peripheral blood monocytes, fibroblasts and human umbilical vein endothelial cells (HUVEC) were investigated for the expression of factor‐H mRNA. In RNA preparations from extrahepatic tissue, factor‐H mRNA was only detected in biopsies from the lung. Using 20 μg total RNA isolated from all 13 cell lines it was not possible to detect any factor‐H mRNA, while mRNA for factor H was expressed in monocytes, HUVEC and fibroblasts.When expressed in extrahepatic tissues, only the 4.3‐kb and the 1.8‐kb mRNA species were detected, while the 1.4‐kb mRNA is expressed abundantly in liver. Interferon‐γ did not induce the expression of factor‐H mRNA in any of the cell lines tested. On the other hand, tumour necrosis factor‐α induced the expression of the 4.3‐kb mRNA species in U937 cells.In HUVEC and fibroblasts the relative quantities of the 4.3‐kb and the 1.8‐kb mRNA species and the regulatory effects of interferon‐γ, interleukin‐1, dexamethasone and retinoic acid on their expression showed significant tissue specificity.
The cytosolic and glycosomal isoenzymes of glyceraldehyde‐3‐phosphate dehydrogenase in Trypanosoma brucei have a distant evolutionary relationship
Authors: MICHELS Paul A. M. , MARCHAND Martine , KOHL Linda , ALLERT Sylvie , WIERENGA Rik K. , OPPERDOES Fred R. 
Published: March 2005

Trypanosoma brucei contains two isoenzymes for glyceraldehyde‐3‐phosphate dehydrogenase: one enzyme resides in a microbody‐like organelle, the glycosome; the other is found in the cytosol. Previously we have reported the characterization of the gene for the glycosomal enzyme [Michels, P. A. M., Poliszczak, A., Osinga, K. A., Misset, O., Van Beeumen, J., Wierenga, R. K., Borst, P. & Opperdoes, F. R. (1986) EMBO J. 5, 1049–1056]. Here we describe the cloning and analysis of the gene that codes for the cytosolic isoenzyme. The gene encodes a polypeptide of 330 amino acids, with a calculated molecular mass of 35440 Da. The two isoenzymes are only 55% identical. The cytosolic glyceraldehyde‐3‐phosphate dehydrogenase differs from the glycosomal enzyme in the following respects: (a) its subunit molecular mass is 3.4 kDa smaller due to the absence of insertions and a small C‐terminal extension which are unique to the glycosomal protein; (b) the cytosolic enzyme has a lower pI (7.9, as compared to 9.3 for the glycosomal isoenzyme), which is due to a reduction in the excess of positively charged amino acids (the calculated net charges of the polypeptides are + 2 and + 11, respectively).We have compared the amino acid sequences of the two T. brucei glyceraldehyde‐3‐phosphate dehydrogenases, with 24 available sequences of the corresponding enzyme of other organisms from various phylogenetic groups. On the basis of this comparison an evolutionary tree was constructed. This analysis strongly supports the theory that T. brucei diverged early in evolution from the main eukaryotic branch of the phylogenetic tree. Further, two separate branches for the lineages leading to Trypanosoma are inferred from the amino acid sequences, suggesting that the genes for the two glyceraldehyde‐3‐phosphate dehydrogenases of the trypanosome are distantly related and must have been acquired independently by the trypanosomal ancestor. The branching determined with the glycosomal enzyme precedes that found with the cytosolic enzyme. The available data do not allow us to decide which of the two genes originally belonged to the trypanosome lineage and which entered the cell later by horizontal gene transfer.
The solution structure of human transforming growth factor α
Authors: HARVEY Timothy S. , WILKINSON Anthony J. , TAPPIN Michael J. , COOKE Robert M. , CAMPBELL Iain D. 
Published: March 2005

The solution structure of transforming growth factor α has been determined by a combination of highresolution 1H‐nuclear magnetic resonance and distance geometry and restrained molecular dynamics. The 382 restraints derived from the NMR experiments were used to calculate many distance geometry structures, which were then refined by restrained molecular mechanics. Five of these structures were further refined using a variety of methods.Comparison of independently measured parameters, such as calculated hydrogen bonding patterns and experimental amide exchange rates, have been used to evaluate the accuracy of the structures. Also, possible mechanisms to explain the pH‐dependent conformational interconversion observed are suggested.Finally comparisons between this work and others on this topic have been made.
Identification of possible two‐reactant sources of oscillations in the Calvin photosynthesis cycle and ancillary pathways
Authors: RYDE‐PETTERSSON Ulf 
Published: March 2005

A systematic search for possible sources of experimentally observed oscillations in the photosynthetic reaction system has been performed by application of recent theoretical results characterizing the transient‐state rate behaviour of metabolic reactions involving two independent concentration variables. All subsystems involving two independent reactants in metabolically fundamental parts of the Calvin cycle and the ancillary pathways of starch and sucrose synthesis have been examined in order to decide on basis of their kinetic and stoichiometric structure whether or not they may trigger oscillations.The results show that no less than 20 possible oscillators can be identified in the examined reaction system, only three of which have been previously considered as potential sources of experimentally observed oscillations. This illustrates the superiority of the method now applied over those previously used to identify possible two‐reactant sources of metabolic oscillations and indicates that there should be no difficulty in complex metabolic pathways to point to a multitude of interactions that may trigger an oscillatory rate behaviour of the system.
A study of the control of NADP+‐dependent isocitrate dehydrogenase activity during gonadotropin‐induced development of the rat ovary
Authors: JENNINGS Gary Thomas , STEVENSON Patricia Margaret 
Published: March 2005

The concentration of cytoplasmic NADP+‐dependent isocitrate dehydrogenase increased 20.2‐fold during gonadotropin‐induced development of the immature rat ovary. Measurement was by protein (Western) blotting using polyclonal antibodies raised against purified enzyme from the porcine corpus luteum. The increase in enzyme concentration during development correlated well with the 18.5‐fold increase observed for the specific activity of the enzyme in the cytosolic fraction.An immunochemical similarity was demonstrated between the cytoplasmic enzyme from the ovary, testes, placenta, skeletal muscle, brain, liver, kidney, mammary and adrenal gland. However the mitochondrial NADP+‐dependent isocitrate dehydrogenase from these tissues was found to be immunochemically distinct from the cytoplasmic enzyme.The concentration of the substrate d(±)‐threo‐isocitrate in the ovaries was measured by fluorometry and found to increase 3.1‐fold during hormone‐induced development. The intracellular concentration of substrate was estimated to be of the same order of magnitude as the enzyme concentration.We conclude that the increase in cytoplasmic NADP+‐dependent isocitrate dehydrogenase activity observed during the gonadotropin‐stimulated development of the rat ovary is due to increased concentration of enzyme rather than to an activation of the enzyme. The activity of the enzyme in vivo appears to be regulated by the availability of the substrate d(±)‐threo‐isocitrate.
Petunia peroxidase a: isolation, purification and characteristics
Authors: HENDRIKS Theo , WIJSMAN Henri J. W. , van LOON Leendert C. 
Published: March 2005

The fast‐moving anionic peroxidase isoenzyme variant PRXa was purified from leaves of petunia (Petunia hybrida). Over 1300‐fold purification was achieved by subjecting extracellular extracts to two sequential acetone precipitations and resuspending the pellets at pH 5.0 and pH 8.0, respectively, followed by gel filtration and chromatofocusing. The purified enzyme had an absorbance ratio (A405 nm/A280 nm) of 3.6, a molecular mass of about 37 kDa and a pI of 3.8. Three molecular forms with slightly different molecular masses were separated by concanavalin‐A–Sepharose affinity chromatography, indicating that these three forms differ in their carbohydrate moieties.The absorption spectrum of PRXa had maxima at 496 and 636 nm and a Soret band at 405 nm. Spectra of compounds I and IV were obtained by titrating a batch of PRXa stored for several months at ‐20°C with H2O2. The addition of 1 mol H2O2/mol freshly purified PRXa caused the formation of compound II, indicating that freshly isolated PRXa contains a bound hydrogen donor which is lost upon storage. Compound III was obtained from both preparations in the presence of excess H2O2.The pH optimum of PRXa for the reaction with H2O2 and guaiacol was 5.0 and its specific activity 61 mkat/g protein. Among various aromatic compounds, coniferyl alcohol was polymerized by PRXa to presumed lignin‐like material. The extracellular localization and high affinity of PRXa for the cinnamic acid derivatives suggest that this isoenzyme functions in the polymerization or cross‐linking of lignin in the plant cell wall.
Heterogeneity of the complex N‐linked oligosaccharides at specific glycosylation sites of two secreted carrot glycoproteins
Authors: STURM Arnd 
Published: March 2005

The N‐linked glycans from the 52/54‐kDa medium protein and cell wall β‐fructosidase, two glycoproteins secreted by carrot suspension culture cells, were characterized. Carrot cells were labelled with [3H]glucosamine or [3H]fucose. The 52/54‐kDa medium protein was isolated form the culture medium and β‐fructosidase from cell walls. The purified proteins were digested with trypsin and glycopeptides were isolated and sequenced. Glycans obtained from individual glycopeptides were separated by gel filtration chromatography and characterized by concanavalin A chromatography, by treatments with exoglycosidases and by sugar composition analysis.The 52/54‐kDa medium protein and cell wall β‐fructosidase have one high‐mannose‐type glycan similar to those from yeast and animal glycoproteins. In addition, the 52/54‐kDa medium protein has three complex‐type and cell wall β‐fructosidase two complex‐type glycans per polypeptide. The complex‐type glycans isolated from individual glycosylation sites are fairly large and very heterogeneous. The smallest of these glycans has the structure [Xyl](Man)3[Fuc](GlcNAc]2Asn (square brackets indicating branching) whereas the larger ones carry additional sugars like terminal N‐acetylglucosamine and possibly rhamnose and arabinose in the case of the 52/54‐kDa medium protein and only arabinose in the case of cell wall β‐fructosidase. These terminal sugars are linked to the α‐mannose residues of the glycan cores. The 52/54‐kDa medium protein is secreted with large and homogeneous complex glycans, their heterogeneity originates from slow processing after secretion. The complex glycans from cell wall β‐fructosidase are processed before the enzyme is integrated into the cell wall.
Uptake of iron by apoferritin from a ferric dihydrolipoate complex
Authors: BONOMI Francesco , PAGANI Silvia 
Published: March 2005

A study was made on the uptake of iron by horse spleen apoferritin, by using as an iron source the same ferric dihydrolipoate complex which represents the major product in the anaerobic removal of ferritin‐bound iron by dihydrolipoate at neutral pH. The ferric dihydrolipoate complex was chemically synthesized and used as an iron donor to apoferritin.Iron uptake was studied, at slightly alkaline pH and in anaerobic conditions, as a function of the concentration of both the iron donor and apoferritin. Isolation of ferritin from mixtures of ferric dihydrolipoate and apoferritin, and subsequent identification of the oxidation state of ferritin‐bound iron, showed that the first metal atoms were taken up in the ferrous form and that this early step was accompanied by accumulation of ferric iron.Total iron uptake increased with the molar ratio of complex to apoprotein and ranged over 25–40% of the iron being supplied. The amount of ferrous iron found inside the protein did not exceed 50–60 mol iron/mol ferritin after a 48‐h incubation. At this time, ferric iron represented a significant fraction of the iron found in the isolated ferritin. Analytical and spectroscopic data indicated that fractional rates and equilibria for disassembly of the ferric complex in the presence of apoferritin were independent of the concentration of the protein and of the complex itself.
Three‐dimensional structure of fatty‐acid‐binding protein from bovine heart
Authors: MÜLLER‐FAHRNOW Anke , EGNER Ursula , JONES T. Alwyn , RÜDEL Heinz , SPENER Friedrich , SAENGER Wolfram 
Published: March 2005

The complex of fatty‐acid‐binding protein (FABP) from bovine heart (cFABP, pI 4.9) with endogenous lipid was crystallized in the presence of ammonium sulfate as precipitant. The needle‐shaped crystals belong to the monoclinic space group C2, with unit‐cell constants a= 5.262(6) nm, b= 7.631(8) nm, c= 3.945(5) nm and β= 94.47(9)°. A native data set to 0.35 nm resolution was collected using synchrotron radiation and film methods.An initial model for the three‐dimensional structure of the protein was constructed based on the crystal structure of the related bovine P2 myelin protein [Jones, T. A., Bergfors, T., Sedzik, J. & Unge, T. (1988) EMBO J. 7, 1597–1604] to which the amino acid sequence of bovine cFABP was adapted. Energy minimizations were carried out under different conditions using both an all‐atom and a united‐atom force field.The optimized models were used to determine the crystal structure of cFABP by molecular‐replacement techniques. The structure was refined by simulated annealing to R= 0.267. As the bound lipid is heterogeneous, it could not be located in the electron‐density map and/or the attained resolution was not sufficient. Bovine cFABP is composed of ten antiparallel β strands forming a β barrel, and by two α helices. The structural features are similar to those of other members of the superfamily of hydrophobic molecule transporters.
Evidence for glycosylphosphatidylinositol anchoring of intralumenal alkaline phosphatase of the calf intestine
Authors: HOFFMANN‐BLUME Eva , GARCIA MARENCO Marvin B. , EHLE Heidrun , BUBLITZ Renate , SCHULZE Margarete , HORN Anton 
Published: March 2005

Considerable amounts of intestinal alkaline phosphatase (AP) were found intralumenally in all animal species investigated, i.e. calf, pig, goat, rat, mouse, guinea pig, hen and carp. The ratios between the total activity of AP found intralumenally and the total intestinal activity vary considerably. Calves and pigs show the highest, i.e. 0.77 and 0.44, respectively, while rodents have much lower ratios. Only 20–34% of the intralumenal alkaline phosphatase (IAP) of the calf and pig is soluble and not within the sediment after centrifugation at 135000 ×g for 60 min, whereas the IAP of rodents is soluble in the range of 60–72% of the total IAP.
For the IAP of the mucosa and chyme of calf, all criteria were found which are generally used, indicating a glycosylphosphatidylinositol (GlcPtdIns) anchor as proved by strong hydrophobicity using Triton X‐114 phase partitioning, phenyl‐Sepharose binding and enzyme aggregation, and the susceptibility to phosphatidylinositol‐specific phospholipase C (PtdIns‐PLC) and papain digestion.
More than 80% of the mucosa alkaline phosphatase (MAP) of the proximal part of the intestine and of the particulate fraction of IAP exhibit these criteria indicating the presence of the GlcPtdIns‐anchor structure, whereas the anchor content of the soluble intralumenal enzyme decreases from the pylorus to the ileocecal junction.
MAP partially purified to a specific activity of 1747 IU/mg retains the anchor structure.
The results presented indicate that the release of large amounts of AP into the chyme is realized without splitting the GlcPtdIns anchor. The possible intralumenal function of this form of AP is discussed.
S‐Adenosylmethionine decarboxylase from the thermophilic archaebacterium Sulfolobus solfataricus
Authors: CACCIAPUOTI Giovanna , PORCELLI Marina , DE ROSA Mario , GAMBACORTA Agata , BERTOLDO Costanzo , ZAPPIA Vincenzo 
Published: March 2005

S‐Adenosylmethionine decarboxylase from Sulfolobus solfataricus, a thermoacidophilic archaebacterium optimally growing at 87°C, has been purified to homogeneity. The specific activity of the homogeneous enzyme is 12 nmol CO2 formed min−1 (mg protein)−1 and the overall yield 8%. The enzyme is thermophilic with an optimum at 75°C, is thermostable, and does not require divalent cations or putrescine for activity. It has a molecular mass of 32 kDa, and appears to be a monomeric protein. S‐Adenosylmethionine decarboxylase from S. solfataricus contains covalently linked pyruvate as prosthetic group and is inactivated in a time‐dependent process by NaCNBH3, in the presence of both the substrate and the product. Incubation with decarboxylated S‐adenosyl[Me‐3H]methionine and NaCNBH3 resulted in the labeling of the protein at the active site.
Molecular cloning of the human α6 integrin subunit
Authors: HOGERVORST Frans , KUIKMAN Ingrid , VAN KESSEL Ad Geurts , SONNENBERG Arnoud 
Published: March 2005

We have isolated cDNAs encoding the α6 subunit from a γ gt11 expression library from human keratinocytes by combined screening with a rabbit polyclonal anti‐α6 antibody and the polymerase chain reaction. The α6 subunit encoded by this cDNA consists of 1050 amino acids with a 991‐amino‐acid extracellular, a 23‐amino‐acid transmembrane and a 36‐amino‐acid cytoplasmic domain. The extracellular domain contains three putative divalent cation‐binding sites and nine potential N‐linked glycosylation sites. From a cDNA library from normal human mammary gland cells two different cDNAs for α6 were isolated, one of which is identical to the above cDNA. The two α6 subunits, called α6A and α6B, encoded by the two cDNAs each have a unique cytoplasmic domain, that of α6B being 18 amino acids longer than that of α6A.Different carcinoma cell lines contain transcripts for both α6 subunits. K 562 leukemic cells have little α6A or α6B mRNAs. The overall level of expression varies in the carcinoma cell lines, but reflects α6 cell surface expression. In A375 melanoma cells, however, cell surface expression of α6 was low in spite of a high level of mRNA. This suggests that other mechanisms may be involved in regulating the expression of α6 on the surface of these cells. The mRNA for both α6 subunits is around 6 kb.The α6 subunits are similar to other α subunits (26–31% identity with cleaved α subunits) of the integrin family but they are more similar to the α3 subunit (40% identity). This high degree of similarity may be the basis for their functional resemblance since both α3 and α6 subunits, when associated with β1, function as laminin receptors and bind to the long arm of laminin. The genes for α6 and β4, the alternative β subunit with which α6 combines on certain epithelial cells, were mapped to chromosome 2 and 17q11‐qter, respectively.
Effects of dexamethasone and cAMP on tyrosine aminotransferase expression in cultured fetal rat hepatocytes
Authors: SHELLY Leslie L. , YEOH George C. T. 
Published: March 2005

Fetal hepatocyte cultures were used to investigate tyrosine aminotransferase (TyrAT) expression during development. Previous studies showed that TyrAT is synthesized by hepatocytes isolated from 15‐day‐gestation fetuses maintained in culture for two or more days, then exposed to dexamethasone. TyrAT expression was essentially undetectable on the first day of culture of hepatocytes derived from 15‐day‐gestation, or less mature, fetuses. Dexamethasone and cAMP are potent inducers of TyrAT and they synergistically induce TyrAT to extremely high levels when added simultaneously to cultured fetal hepatocytes.The effects of dibutyryl‐cAMP (Bt2cAMP) alone and in combination with dexamethasone on TyrAT expression are investigated. Hepatocytes isolated from 15‐day‐gestation fetuses exposed to both inducers possessed detectable levels of TyrAT activity and mRNA on day 1 of culture, and this increased by day 3. In contrast, hepatocytes exposed to either inducing agent alone were essentially negative on day 1, but positive on day 3. This was shown to be a consequence of transcription. When 13‐day‐gestation hepatocytes were maintained in culture under identical conditions detectable levels of TyrAT mRNA were evident on day 1, and this increased by day 3.Immunocytochemical studies revealed that the appearance and subsequent increase in TyrAT production elicited by dexamethasone and Bt2cAMP were due to changes in the proportion of hepatocytes expressing the enzyme. Therefore, in the presence of both dexamethasone and Bt2cAMP, TyrAT expression can be detected in some cells at an earlier stage of liver development than reported previously.