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991.
1-acid glycoprotein (AGP) is a serum acute phase glycoprotein which possesses five N-linked complex type heteroglycan side chains which may be present as bi-, tri- and tetraantennary structures. Depending upon the content of biantennary structure on AGP, up to four glycoforms of AGP are present in serum. These glycoforms can be easily estimated in body fluids by means of crossed affinity-immunoelectrophoresis (CAIE) with the lectin, Concanavalin A (Con A). Con A selectively binds biantennary structures; the more biantennary structures on AGP, the stronger the binding. In acute inflammation, a relative increase of AGP glycoforms with biantennary units is observed - a type I glycosylation change. In some chronic inflammatory states there is an relative decrease of AGP glycoforms with biantennary heteroglycans — a type II glycosylation change. Moreover, in certain other states such as pregnancy, estrogen administration or liver damage, type II glycosylation changes are also seen. A detailed analysis of the clinical applications of the assessment of AGP glycoforms in sera of patients with rheumatic diseases, AIDS and various types of cancers is presented. Accumulated data shows that AGP glycoforms may be very useful in the detection of intercurrent infections in the course of rheumatoid arthritis, systemic lupus erythematosus, or myeloblastic leukaemia, and in the detection of secondary infections in human immunodeficiency virus infected individuals. AGP glycoforms are also very useful in differentiation between various forms of trophoblastic disease and are helpful in monitoring the treatment of these patients. Finally, AGP glycoforms provide valuable information for differentiation between primary and secondary liver cancer. 相似文献
992.
993.
Sujoy Ghosh John W. Kyle Sara Dastgheib Francois Daussin Zhixiong Li Subhash Basu 《Glycoconjugate journal》1995,12(6):838-847
A 1-3 galactosyltransferase (GalT-3; UDP-Gal; GM2 1-3galactosyltransferase) was purified over 5100-fold from 19-day-old embryonic chicken brain homogenate employing detergent solubilization, -lactalbumin Sepharose, Q-Sepharose, UDP-hexanolamine Sepharose, and GalNAc1-4Gal-Synsorb column chromatography. The purified enzyme was resolved into two bands on reducing gels with apparent molecular weights of 62 kDa and 65 kDa, respectively. GalT-3 activity was also localized in the same regions by activity gel analysis and sucrose-density gradient centrifugation of a detergent-solubilized extract of 19-day-old embryonic chicken brain. Purified GalT-3 exhibited apparentK
mS of 33 µm, 22 µm and 14.4mM with respect to the substrates GM2, UDP-galactose, and MnCl2, respectively. Substrate specificity studies with the purified enzyme and a variety of glycosphingolipids, glycoproteins, and synthetic substrates revealed that the enzyme was highly specific only for the glycosphingolipid acceptors, GM2 and GgOse3Cer (asialo-GM2). Ovine-asialo-agalacto submaxillary mucin inhibited the transfer of galactose to GM2 but did not act as an acceptor in the range of concentrations tested. Polyclonal antibodies raised against purified GalT-3 inhibited GalT-3 activityin vitro and Western-immunoblot analysis of purified GalT-3 showed immunopositive bands at 62 and 65 kDa.Abbreviations CNS
central nervous system
- GM1
monosialotetraosylganglioside, Gal1-3GalNAc1-4(NeuAc2-3)Gal1-4Glc1-1Cer
- GM2
monosialotriaosylganglioside, GalNAc1-4(NeuAc2-3)Gal1-4Glc1-1Cer
- DSS
detergent solubilized supernatant
- ECB
embryonic chicken brain
- TBS
Tris-buffered saline 相似文献
994.
Molecular dynamics simulations and energy analysis have been carried out to study the structural mobility and stability of the four -helix bundle motifs. The simulation results as well as the X-ray data show that the atomic RMS fluctuation is larger at the loop region for four representative proteins investigated: methemerythrin, cytochrome b-562, cytochrome c, and bovine somatotropin. The loop-loop, helix-helix, and loop-helix interactions are computed for the unfolded and folded proteins. In the folded and solvated protein structures the loop-helix interaction is stronger than the helix-helix interaction, especially in the electrostatic component. But the stabilization energies of both the loop-helix and the helix-helix interactions relative to the those of an unfolded structure are of the same order of magnitude. The stabilization due to protein-solvent interaction is greater in the helix region than in the loop region. The percentage of hydrophilic solvent accessible area for the four proteins studied was calculated with the method of Eisenberg and McLachlan. The percentage of the hydrophilic area is greater in the loops than in the helices. A Poisson-Boltzmann calculation shows that the potential from the loops acting on a helix is generally more negative than that from other helices. 相似文献
995.
Thomas J. Thekkumkara Jing Du John C. Zwaagstra Kathleen M. Conrad John Krupinski Kenneth M. Baker 《Molecular and cellular biochemistry》1995,152(1):77-86
G-protein coupled Angiotensin II receptors (AT1A), mediate cellular responses through multiple signal transduction pathways. In AT1A receptor-transfected CHO-K1 cells (T3CHO/AT1A), angiotensin II (AII) stimulated a dose-dependent (EC50=3.3 nM) increase in cAMP accumulation, which was inhibited by the selective AT1, nonpeptide receptor antagonist EXP3174. Activation of protein kinase C, or increasing intracellular Ca2+ with ATP, the calcium ionophore A23187 or ionomycin failed to stimulate cAMP accumulation. Thus, AII-induced cAMP accumulation was not secondary to activation of a protein kinase C- or Ca2+/calmodulin-dependent pathway. Since cAMP has an established role in cellular growth responses, we investigated the effect of the AII-mediated increase in cAMP on cell number and [3H]thymidine incorporation in T3CHOA/AT1A cells. AII (1 M) significantly inhibited cell number (51% at 96 h) and [3H]thymidine incorporation (68% at 24 h) compared to vehicle controls. These effects were blocked by EXP3174, confirming that these responses were mediated through the AT1 receptor. Forskolin (10 M) and the cAMP analog dibutyryl-cAMP (1 mM) also inhibited [3H]thymidine incorporation by 55 and 25% respectively. We extended our investigation on the effect of AII-stimulated increases in cAMP, to determine the role for established growth related signaling events, i.e., mitogen-activated protein kinase activity and tyrosine phosphorylation of cellular proteins. AII-stimulated mitogen-activated protein kinase activity and phosphorylation of the 42 and 44 kD forms. These events were unaffected by forskolin stimulated increases in cAMP, thus the AII-stimulated mitogen-activated protein kinase activity was independent of cAMP in these cells. AII also stimulated tyrosine phosphorylation of a number of cellular proteins in T3CHO/AT1A cells, in particular a 127 kD protein. The phosphorylation of the 127 kD protein was transient, reaching a maximum at 1 min, and returning to basal levels within 10 min. The dephosphorylation of this protein was blocked by a selective inhibitor of cAMP dependent protein kinase A, H89-dihydrochloride and preexposure to forskolin prevented the AII-induced transient tyrosine phosphorylation of the 127 kD protein. These data suggest that cAMP, and therefore protein kinase A can contribute to AII-mediated growth inhibition by stimulating the dephosphorylation of substrates that are tyrosine phosphorylated in response to AII. 相似文献
996.
Anne L. Holleran Donald A. Briscoe Gary Fiskum Joanne K. Kelleher 《Molecular and cellular biochemistry》1995,152(2):95-101
A study was undertaken to assess the role of a physiological concentration of glutamine in AS-30D cell metabolism. Flux of14C-glutamine to14CO2 and of14C-acetate to glutamate was detected indicating reversible flux between glutamate and TCA cycle -ketoglutarate. These fluxes were transaminase dependent. A flux analysis was compared using data from three tracers that label -ketoglutarate carbon 5, [2-14C]glucose, [1-14C]acetate and [5-14C]glutamine. The analysis indicated that the probability of flux of TCA cycle -ketoglutarate to glutamate was, at minimum, only slightly less than the probability of flux of -ketoglutarate through -ketoglutarate dehydrogenase. The apparent Km for oxidative flux of [14C]glutamine to14CO2, 0.07 mM, indicated that this flux was at a maximal rate at physiological, 0.75 mM, glutamine. Although oxidative flux through -ketoglutarate dehydrogenase was the major fate of glutamine, flux of glutamine to lipid via reductive carboxylation of -ketoglutarate was demonstrated by measuring incorporation of [5-14C]glutamine into14C-lipid. In media containing glucose (6 mM), and glutamine (0.75 mM) 47 per cent of the lipid synthesized from substrates in the media was derived from glutamine via reductive carboxylation and 49 per cent from glucose. These findings of nearly equal fluxes suggest that lipogenesis via reductive carboxylation may be an important role of glutamine in hepatoma cells. 相似文献
997.
Michael Böhm 《Molecular and cellular biochemistry》1995,147(1-2):147-160
Alterations of receptor-G-protein-regulated adenylyl cyclase activity have been suggested to represent an important alteration leading to contractile dysfunction in the failing human heart. Recent experiments suggest that the 1-adrenoceptor(1AR) density and mRNA levels are reduced, while 2-adrenoceptors and stimulatory G-proteins are unchanged (mRNA and protein level). Functional assays demonstrated that the catalyst of the adenylyl cyclase is not different between failing and nonfailing myocardium. Inhibitory G-proteins are increased (pertussis toxin substrates, protein and mRNA) and correlate to the reduced inotropic effects of -adrenoceptor agonists and of CAMP-PDE inhibitors. Gi-coupled m-cholinoceptors and A1-adrenergic receptors are unchanged in density and affinity. Stimulation of these receptors resulted in an unchanged antiadrenergic effect on force of contraction. In conclusion, a downregulation of 1-AR and an increase of Gi have been observed as signal transduction alteration in failing human myocardium. These alterations are due to alterations of gene expression in the failing heart and are related to a defective regulation of force of contraction in heart failure. 相似文献
998.
François-Yves Dupradeau Guillaume Le Flem Jean-Michel Wieruszeski Manuel Dauchez Alain Alix Véronique Larreta-Garde Jean-Pierre Monti 《Letters in Peptide Science》1997,4(4-6):489-495
H-NMR studies of the bovine insulin S-sulfonatedB-chain are reported in H2O/D2O (9/1) and inglycerol-d5 (5 M) using two-dimensional NMRspectroscopy. The first results show that the oxidizedinsulin B-chain secondary structure differs from thatof native insulin by a loss of the -helixbetween the two disulfide bridges and that theglycerol favours the structuring of the peptide. 相似文献
999.
Christelle David Laurent Bischoff Hervé Meudal Catherine Llorens-Cortes Bernard Pierre Roques Marie-Claude Fournié-Zaluski 《Letters in Peptide Science》1997,4(4-6):411-414
In order to study the physiological role of aminopeptidase A (APA),several -mercapto--amino acyl dipeptides were synthesized toobtain compounds having a high affinity for APA and a high selectivityversus aminopeptidase N (APN). Sulfonamide and carboxylate moieties whichhave been shown to be recognized by the S1 subsite of theenzyme were introduced on the side chain of the -mercapto--aminoacyl sub-unit, the latter being coupled to dipeptides optimized to interactwith the S1 andS2 subsites by means of combinatorialchemistry. Good affinities (16 nM) were obtained, the selectivity factorsbeing up to 160-fold versus APN. 相似文献
1000.
Petra Düx Brian Whitehead Rolf Boelens Robert Kaptein Geerten W. Vuister 《Journal of biomolecular NMR》1997,10(3):301-306
A modified HNHB experiment is presented that allows thedetermination of J(NH) coupling constants directly from the ratio ofcross-peak to diagonal-peak intensities. The experiment was applied to thephotoactive yellow protein (PYP) and yielded the magnitude of 1173J(NH) coupling constants. In addition, 293J(NH(i–1)) coupling constantscould be measured, providing information about the backbone angle .These data, in conjunction with the magnitudes of the3J(HNH) coupling constantsobtained from the HNHA spectrum, effectively discriminate the twopossibilities for the stereospecific assignment of theH resonances in glycine residues. For all eight glycineresidues in PYP that were not subject to conformational averaging and hadnon-degenerate H resonance frequencies, the J-couplingdata, together with limited NOE data, yielded the stereospecific assignmentof the H resonances for these residues. In addition,reliable and precise , dihedral constraints were also derived forthese residues from the J-coupling data. 相似文献