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981.
We used a spin-labeled ATP analog, SL-ATP, to study nucleotide binding to highly purified human multidrug resistance protein
3, MRP3, which had been expressed in the yeast Pichia pastoris. SL-ATP was shown to be a good substrate analog and is hydrolyzed by MRP3 at about 10% of the Vmax for normal ATP. ESR titrations
showed that 2 mol of SL-ATP readily bound per mole of MRP3 with a dissociation constant of about 100 μM in the presence of
Mg2+ ions. The binding curve was easily fitted for a hyperbolic binding relationship. SL-ATP also bound readily to MRP3 in the
absence of divalent ions and presence of EDTA. The resulting binding curve, however, could not be satisfactorily fitted using
the equation for hyperbola. Analysis showed that a good fit was only obtained with the Hill equation using a Hill coefficient
of 4 or close to 4. Lower Hill coefficients resulted in lower goodness of the fit. Such cooperative binding may be explained
by a dimerization event triggered in the absence of divalent ions and a close communication of nucleotide binding sites of
the interacting dimers. These findings may be of great importance for the overall mechanism and regulation of multidrug resistance
proteins. 相似文献
982.
Ina Fabian Ilan Bleiberg Moshe Aronson 《Biochimica et Biophysica Acta (BBA)/General Subjects》1978,544(1):69-76
Heparin uptake and desulphation by cultured macrophages were investigated. Histones, polyamino-acids, protamine and eosinophil-basic protein stimulated both heparin uptake and desulphation, processes found to be non-related. Poly-l-ornithine and poly-dl-lysine increased the heparin uptake by about 33-fold, and histone produced up to 7.5-fold increase in the desulphation. The same polycations inhibited heparin desulphation by macrophage extracts. 相似文献
983.
Gabriela Meirelles Amanda Valle Pinhatti Daniel Sosa-Gomez Luis Mauro Gonçalves Rosa Sandra B. Rech Gilsane Lino von Poser 《Plant Cell, Tissue and Organ Culture》2013,112(3):379-385
Changes in biomass and bioactive metabolites after treatment with the fungus Nomuraea rileyi (Farlow) Samson added as dried culture (DC) or as dried autoclaved cell powder (DACP) for short and long periods of time have been investigated in Hypericum polyanthemum plants grown under controlled conditions and after 18 weeks of field acclimatization. Plants grown under controlled conditions and treated with DACP showed increased concentrations of the benzopyrans HP1 (6-isobutyryl-5,7-dimethoxy-2,2-dimethylbenzopyran), HP2 (7-hydroxy-6-isobutyryl-5-methoxy-2,2-dimethylbenzopyran), and HP3 (5-hydroxy-6-isobutyryl-7-methoxy-2,2-dimethylbenzopyran) while DC affected negatively or did not alter the synthesis of these compounds. Lower levels of the phloroglucinol derivative uliginosin B were detected in all treatments. Long time treatment with DACP of acclimatized plants triggered doubling of biomass as compared to control and chemical analyses demonstrated significant increase on total phenolic compounds in vegetative parts of plants. Moreover, the higher performance liquid chromatography analysis showed different pattern of metabolites accumulation, with higher yields of HP1, HP2, HP3 and uliginosin B in the reproductive parts of the plants treated with DACP during all experiments. The elevation of bioactive metabolites levels in response to the elicitor suggests that these compounds are inducible as part of the defense response of H. polyanthemum. 相似文献
984.
The chlorophyll-protein complexes of the yellow alga Synura petersenii (Chrysophyceae) and the yellow-green alga Tribonema aequale (Xanthophyceae) were studied. The sodiumdodecylsulfate/sodiumdesoxycholate solubilized photosynthetic membranes of these species yielded three distinct pigment-protein complexes and a non-proteinuous zone of free pigments, when subjected to SDS polyacrylamid gel electrophoresis. The slowest migrating protein was identical to complex I (CP I), the P-700 chlorophyll a-protein, which possessed 60 chlorophyll a molecules per reaction center in Tribonema and 108 in Synura. The zone of intermediate mobility contained chlorophyll a and carotenoids. The absorption spectrum of this complex was very similar to the chlorophyll a-protein of photosystem II (CP a), which is known from green plants. The fastest migrating pigment protein zone was identified as a light-harvesting chlorophyll-protein complex. In Synura this protein was characterized by the content of chlorophyll c and of fucoxanthin. Therefore this complex will be named as LH Chl a/c-fucocanthin protein. In addition to the separation of the chlorophyll-protein complexes the cellular contents of P-700, cytochrome f (bound cytochrome) and cytochrome c-553 (soluble cytochrome) were measured. The stoichiometry of cytochrome f: cytochrome c-553:P-700 was found to be 1:4:2.4 in Tribonema and 1:6:3.4 in Synurá.Abbreviations CP a
chlorophyll a-protein of photosystem II
- CP I
P-700 chlorophyll a-protein
- FP
free pigment
- LH Chl a/c
light-harvesting chlorophyll a/c-protein
- PAGE
polyacrylamidgelelectrophoresis
- SDS
Sodiumdodecylsulfate
- SDOC
sodium-desoxycholate 相似文献
985.
986.
987.
Ina Schulte E-juan Zhang Zhong-ji Meng Rong-juan Pei Mengji Lu Michael Roggendorf 《中国病毒学》2008,23(2):107-115
The woodchuck model is an excellent animal model to study hepadnaviral infection. The new progresses in this model made possible to examine the T-cell mediated immune responses in acute and chronic hepadnaviral infection. Recently, a new assay for cytotoxic T-cells based on detection of CD107 was established for the woodchuck model. In addition, new immunotherapeutic approaches based on combination of potent antiviral treatment and DNA-protein vaccines were proven to be useful for treatment of chronic hepatitis B. 相似文献
988.
989.
Groups of Hodotermes mossambicus reproductives exhibit social behaviour. Maintenance of this behaviour by an individual depends on frequent contact of its body by the antennae of other termites. The antennae of the recipient do not play a rôle. Pairs on the other hand exhibit antisocial behaviour. Development of pair behaviour occurs when antenna to body contact is reduced or absent. Furthermore, at least the proximal parts of the antennae are required for full development of pair behaviour. Pheromones are not implicated in the change from group to pair behaviour. 相似文献
990.