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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
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Anthropogenic disturbances affect temperature in river systems. Temperature potentially affects life histories of macroinvertebrates and alters behavior and biological functions. Temperature preferences and tolerance ranges for key taxa are therefore critical for understanding impacts of human-induced changes to water temperatures on river ecosystems. The objective of this study was to examine the effect of water temperature on growth rate and behavior of Epeorus albertae (McDunnough) nymphs. Nymphs were collected from the Umatilla River in eastern Oregon, and exposed to temperatures of 18, 22, and 28 °C. Nymphs held at 28 °C exhibited increased growth rates compared with individuals held at 18 and 22 °C. However, at 28 °C the accumulation of nymphal tissues was not consistent with that of nymphs held in lower temperatures; ratios of head capsule width to total body length were significantly lower in individuals at 28 °C compared with those held at the lower temperatures. This indicates that the nymphs held at the high temperature had longer total body length relative to the developmental stage, represented by head capsule width, when compared with insects in cooler temperatures. To examine the effect of water temperature on behavior, active drift of mayflies was examined in experimental chambers held at 12, 18, 22, and 28 °C. The number of drifting insects observed was significantly higher at 28 °C compared with 22, 18, and 12 °C. These results indicate that temperature is a factor influencing growth and behavior of E. albertae and is likely to lead to limitations in habitat use of this mayfly. 相似文献
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Imen Tanniche Hadi Nazem-Bokaee David M. Scherr Sara Schlemmer Ryan S. Senger 《Biotechnology progress》2023,39(3):e3324
Bacterial small RNAs (sRNAs) that regulate gene expression have been engineered for uses in synthetic biology and metabolic engineering. Here, we designed a novel non-Hfq-dependent sRNA scaffold that uses a modifiable 20 nucleotide antisense binding region to target mRNAs selectively and influence protein expression. The system was developed for regulation of a fluorescent reporter in vivo using Escherichia coli, but the system was found to be more responsive and produced statistically significant results when applied to protein synthesis using in vitro cell-free systems (CFS). Antisense binding sequences were designed to target not only translation initiation regions but various secondary structures in the reporter mRNA. Targeting a high-energy stem loop structure and the 3′ end of mRNA yielded protein expression knock-downs that approached 70%. Notably, targeting a low-energy stem structure near a potential RNase E binding site led to a statistically significant 65% increase in protein expression (p < 0.05). These results were not obtainable in vivo, and the underlying mechanism was translated from the reporter system to achieve better than 75% increase in recombinant diaphorase expression in a CFS. It is possible the designs developed here can be applied to improve/regulate expression of other proteins in a CFS. 相似文献
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EMMA L. WRIGHT COLIN R. BLACK ALEXANDER W. CHEESMAN TREVOR DRAGE DAVID LARGE BENJAMIN L. TURNER SOFIE SJÖGERSTEN 《Global Change Biology》2011,17(9):2867-2881
Tropical peatlands play an important role in the global carbon cycling but little is known about factors regulating carbon dioxide (CO2) and methane (CH4) fluxes from these ecosystems. Here, we test the hypotheses that (i) CO2 and CH4 are produced mainly from surface peat and (ii) that the contribution of subsurface peat to net C emissions is governed by substrate availability. To achieve this, in situ and ex situ CO2 and CH4 fluxes were determined throughout the peat profiles under three vegetation types along a nutrient gradient in a tropical ombrotrophic peatland in Panama. The peat was also characterized with respect to its organic composition using 13C solid state cross‐polarization magic‐angle spinning nuclear magnetic resonance spectroscopy. Deep peat contributed substantially to CO2 effluxes both with respect to actual in situ and potential ex situ fluxes. CH4 was produced throughout the peat profile with distinct subsurface peaks, but net emission was limited by oxidation in the surface layers. CO2 and CH4 production were strongly substrate‐limited and a large proportion of the variance in their production (30% and 63%, respectively) was related to the quantity of carbohydrates in the peat. Furthermore, CO2 and CH4 production differed between vegetation types, suggesting that the quality of plant‐derived carbon inputs is an important driver of trace gas production throughout the peat profile. We conclude that the production of both CO2 and CH4 from subsurface peat is a substantial component of the net efflux of these gases, but that gas production through the peat profile is regulated in part by the degree of decomposition of the peat. 相似文献
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Srivastava M Scherr H Lackey M Xu D Chen Z Lu J Bergmann A 《Cell death and differentiation》2007,14(1):92-102
In mammals and Drosophila, apoptotic caspases are under positive control of the CED-4-like proteins Apaf-1 and ARK, respectively. In an EMS-mutagenesis screen, we isolated 33 ark mutants as recessive suppressors of hid-induced apoptosis. The ark mutants are loss-of-function alleles characterized by reduced developmental apoptosis. Using the phenotypic series of these alleles, we identified helical domain I in the nucleotide oligomerization domain as critical for ARK's apoptotic activity. Interestingly, the WD40 region may also have an unanticipated positive requirement for the apoptotic activity of ARK. Considering structural information, we discuss the roles of these domains for assembly and activity of the ARK apoptosome, and propose that the WD40 region is anti-apoptotic in the absence of apoptotic signals, and pro-apoptotic in the presence of such signals. Furthermore, a defined null allele reveals that ark is required for most, but not all apoptosis suggesting the existence of an ARK-independent apoptotic pathway. 相似文献
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