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41.
Acceptor specificity of the human leukocyte alpha3 fucosyltransferase: role of FucT-VII in the generation of selectin ligands 总被引:2,自引:2,他引:0
Britten CJ; van den Eijnden DH; McDowell W; Kelly VA; Witham SJ; Edbrooke MR; Bird MI; de Vries T; Smithers N 《Glycobiology》1998,8(4):321-327
The alpha3 fucosyltransferase, FucT-VII, is one of the key
glycosyltransferases involved in the biosynthesis of the sialyl Lewis X
(sLex) antigen on human leukocytes. The sialyl Lewis X antigen
(NeuAcalpha(2-3)Galbeta(1-4)[Fucalpha(1-3)]GlcNAc-R) is an essential
component of the recruitment of leukocytes to sites of inflammation,
mediating the primary interaction between circulating leukocytes and
activated endothelium. In order to characterize the enzymatic properties of
the leukocyte alpha3 fucosyltransferase FucT-VII, the enzyme has been
expressed in Trichoplusia ni insect cells. The enzyme is capable of
synthesizing both sLexand sialyl-dimeric-Lexstructures in vitro , from
3'-sialyl-lacNAc and VIM-2 structures, respectively, with only low levels
of fucose transfer observed to neutral or 3'-sulfated acceptors. Studies
using fucosylated NeuAcalpha(2-3)-(Galbeta(1- 4)GlcNAc)3-Me acceptors
demonstrate that FucT-VII is able to synthesize both di-fucosylated and
tri-fucosylated structures from mono- fucosylated precursors, but
preferentially fucosylates the distal GlcNAc within a polylactosamine
chain. Furthermore, the rate of fucosylation of the internal GlcNAc
residues is reduced once fucose has been added to the distal GlcNAc. These
results indicate that FucT-VII is capable of generating complex selectin
ligands, in vitro , however the order of fucose addition to the lactosamine
chain affects the rate of selectin ligand synthesis.
相似文献
42.
A model of steady-state erythropoiesis in the guinea pig is described. The model incorporates an unidentified progenitor compartment, as well as compartments representing proerythroblasts, basophilic, polychromatic and orthochromatic cells. A computer representation of the model permits a simulation of the labeling curves obtained in pulse and intermittent labeling regimes. It was found that a reasonable fit to the data can be achieved when the parameters for the various compartments are essentially identical. The results of a preliminary sensitivity analysis, carried out by perturbing the duration of S phase from the best fit value, are reported. The fit achieved to the data supports the hypothesis underlying the model that each compartment corresponds to one generation and that the flux within and between compartments is sequential. 相似文献
43.
David A Baldwin Deolinda MR de Sousa 《Biochemical and biophysical research communications》1981,99(4):1101-1107
The kinetics of iron release from N-terminal and C-terminal monoferric human transferrins has been studied using EDTA as the accepting chelate. In the absence of added salts iron release from the N-terminal site is more facile but the relative lability can be reversed by the addition of NaClO4, NaCl and LiCl. The results indicate that both anions and cations can affect the lability of the two sites. Since the relative lability of the two monoferrictransferrins is affected by fairly moderate concentrations of NaCl and NaClO4 we suggest that the ionic composition serum may play an important role in determining the observed distribution of iron among the sites. A new method for the preparation of N-terminal monoferrictransferrin is described. 相似文献
44.
J A Starling B L Allen M R Kaeini D M Payne H J Blytt H W Hofer B G Harris 《The Journal of biological chemistry》1982,257(7):3795-3800
A rapid and efficient procedure has been developed to purify phosphofructokinase from the muscle of the parasitic roundworm, Ascaris suum. The procedure can be accomplished in 1 day with a 420-fold purification and a 60% yield. The enzyme was shown to be homogeneous by two-dimensional electrophoresis, Sepharose 6B column chromatography, and high performance liquid chromatography utilizing a size exclusion column. The subunit molecular weight of the enzyme was found to be 95,000 by electrophoresis in the presence of sodium dodecyl sulfate. In solutions of low ionic strength, the native enzyme aggregated to species of higher molecular weight than did the rabbit muscle phosphofructokinase. In the presence of 0.2 M (NH4)2SO4, the minimum native molecular weight was determined to be 398,000 by high performance liquid chromatography and Sepharose 6B column chromatography. Therefore, the enzyme appears to be a tetramer with identical or near-identical subunits. The apparent isoelectric point of the enzyme was shown to be 7.3 to 7.4 by both column and gel isoelectric focusing. Amino acid analysis revealed a lower number of the aromatic residues Phe, Tyr, and Trp than in the rabbit muscle enzyme and this is in agreement with the lower extinction coefficient of E1%280 nm = 6.5. Analysis of the purified enzyme revealed 7.4 +/- 0.6 mol of phosphate/mol of enzyme. 相似文献
45.
CD95/CD95L interactions are vital to normal lymphoid homeostasis and in the protection against autoimmunity. To directly assess the effects of CD95L on activated B cell survival and Ig responses, purified human peripheral blood B cells, activated in vitro with SAC + rIL2, were incubated with a soluble CD95L fusion protein (fp) and assayed for apoptosis and IgG/IgM production. CD95L fp reproducibly increased apoptosis of these activated B cells and inhibited their Ig production. However, CD95L fp-mediated effects on activated B cell survival could be uncoupled from those on Ig production in that a soluble CD40L fp was incapable of reversing CD95L fp-mediated downregulation of Ig responses despite inhibiting CD95L fp-mediated apoptosis. Moreover, despite the specific caspase-8 inhibitor z-IETD-fmk substantially protecting transformed CL-01 B cells from CD95L fp-mediated apoptosis and permitting their ongoing proliferation, caspase-8 inhibition had no protective effects on CD95L fp-mediated inhibition of constitutive IgM production by CL-01 B cells. Collectively, these results point to a CD95-based downregulatory pathway in activated B cells that need not necessarily culminate in their death. 相似文献
46.
Sianos G Kay IP Carlier SG Lighart JM Wardeh AJ Coen VL Levendag PC Serruys PW 《International journal of cardiovascular interventions》2000,3(2):121-125
The application of beta-radiation in coronary arteries is a promising new technique for the treatment of in-stent restenosis. This is the first case in which the 5 F. delivery catheter of the Beta-Cath trade mark system was advanced through the struts of a stent, previously deployed in an adjacent branch, so as to deliver radiation to the target vessel. 相似文献
47.
Kempson J Pitts WJ Barbosa J Guo J Omotoso O Watson A Stebbins K Starling GC Dodd JH Barrish JC Felix R Fischer K 《Bioorganic & medicinal chemistry letters》2005,15(7):1829-1833
A series of fused pyrimidine based inhibitors of PDE7 have been derived from an earlier screening lead 1. The synthesis, structure-activity relationships (SAR) and selectivity against several other PDE family members are described. 相似文献
48.
49.
Jo?o?Luiz?S?Moreira Rodrigo?M?Mota Maria?F?Horta Santuza?MR?Teixeira Elisabeth?Neumann Jacques?R?Nicoli álvaro?C?NunesEmail author 《BMC microbiology》2005,5(1):15
Background
The accurate identification of Lactobacillus and other co-isolated bacteria during microbial ecological studies of ecosystems such as the human or animal intestinal tracts and food products is a hard task by phenotypic methods requiring additional tests such as protein and/or lipids profiling. 相似文献50.
Fish micronuclei tests (MN) were used to evaluate the ability of wastewater from two municipal sewage treatment plants that empty into Lake Paranoá to cause genetic damage. There were no significant differences in the frequencies of micronuclei between the control and hypertrophic areas. In contrast, cyclophosphamide and mitomycin C, used to test the sensitivity of the biological assay, significantly increased the micronuclei counts in Tilapia rendalli, Oreochromis niloticus and Cyprinus carpio, T. rendalli was the most sensitive specie to both clastogens and C. carpio, the most resistant. 相似文献