排序方式: 共有66条查询结果,搜索用时 31 毫秒
41.
Bacteriophage P1 encodes several regulatory elements for the lytic or lysogenic response, which are located in the immC, immI, and immT regions. Their products are the C1 repressor of lytic functions with the C1 inactivator protein Coi, the C4 repressor of antirepressor synthesis and the modulator protein Bof, respectively. We have studied in vitro the interaction of the components of the immC and immT regions with C1-controlled operators using highly purified Bof, C1, and Coi proteins. Bof protein (M(r) = 9,800) does not interact with C1 repressor alone, but as shown by DNA mobility shift experiments, in the presence of C1 repressor Bof binds to all operators tested by forming a C1.Bof-operator DNA ternary complex. The effect of this complex formation was studied in more detail with the operator of the c1 gene. Here, Bof only marginally alters the C1 repressor footprint at Op99a,b, but nevertheless considerably influences the repressibility of the operator.promoter element: (i) the autoregulated c1 mRNA synthesis is further down-regulated and (ii) the ability of Coi protein to dissociate the C1.operator DNA complex is strongly inhibited. We suggest that Bof protein functions by modulating C1 repression of many widely dispersed operators on the prophage genome. 相似文献
42.
Syndecan-4 is a cell membrane proteoglycan composed of a transmembrane core protein and substituted glycosaminoglycan (GAG) and N-linked glycosylated (N-glycosylated) chains. The core protein has three domains: extracellular, transmembrane and cytoplasmic domains. The GAG and N-glycosylated chains and the cytoplasmic domain of syndecan-4, especially the amino acids: Ser(178) and Tyr(187) are critical in regulation of turkey satellite cell growth and development. How these processes are regulated is still unknown. The objective of the current study was to determine whether the syndecan-4 GAG and N-glycosylated chains and the cytoplasmic domain functions through modulating focal adhesion formation and apoptosis. Twelve mutant clones were generated: a truncated syndecan-4 without the cytoplasmic domain with or without GAG and N-glycosylated chains, and Ser(178) and Tyr(187) mutants with or without GAG and N-glycosylated chains. The wild type syndecan-4 and all of the syndecan-4 mutants were transfected into turkey myogenic satellite cells after which cell apoptosis and focal adhesion formation were measured. Syndecan-4 increased cell membrane localization of β1 integrin and the activity of focal adhesion kinase (FAK) whereas the cytoplasmic domain mutation decreased the phosphorylation of FAK. However, syndecan-4 and syndecan-4 mutants did not influence cell apoptosis. They also had no effect on vinculin or paxillin-containing focal adhesion formation. These results suggested that the syndecan-4 cytoplasmic domain plays an important role in regulating FAK activity and β1 integrin cell membrane localization but not cell apoptosis and vinculin or paxillin-containing focal adhesion formation. 相似文献
43.
Velleman SG McCormick RJ Ely D Jarrold BB Patterson RA Scott CB Daneshvar H Bacon WL 《Experimental biology and medicine (Maywood, N.J.)》2001,226(4):328-333
This study reports the concentration of collagen and its hydroxypyridinoline crosslinks, collagen fibril organization in the dorsal aortas, and systolic blood pressure during the progression of atherosclerosis in Japanese quail selected for cholesterol-induced atherosclerosis. The quail were placed on either a control or 0.5% cholesterol-added diet at approximately 16 weeks of age. The concentration of total collagen did not change in the control arteries during the course of the study, whereas at 5 and 10 weeks of cholesterol feeding, collagen levels decreased in the cholesterol-fed birds. Hydroxypyridinoline concentration increased during the duration of the study in the cholesterol-fed birds and by 15 and 20 weeks of cholesterol feeding, levels were significantly increased over those observed in the control arteries. Transmission electron microscopy showed changes in the organization of collagen fibrils. Increased systolic blood pressure was noted beginning at 10 weeks of cholesterol feeding, which is suggestive of other systemic changes induced by hypercholesterolemia. These results demonstrated remodeling of the collagen component of the dorsal aorta extracellular matrix during the progression of atherosclerosis and are suggestive of other systemic cardiovascular system changes. 相似文献
44.
Evolutionary rates for tuf genes in endosymbionts of aphids 总被引:5,自引:1,他引:4
The gene encoding elongation factor Tu (tuf) in aphid endosymbionts (genus
Buchnera) evolves at rates of 1.3 x 10(-10) to 2.5 x 10(-10) nonsynonymous
substitutions and 3.9 x 10(-9) to 8.0 x 10(-9) synonymous substitutions per
position per year. These rates, which are at present among the most
reliable substitution rates for protein-coding genes of bacteria, have been
obtained by calibrating the nodes in the phylogenetic tree produced from
the Buchnera EF-Tu sequences using divergence times for the corresponding
ancestral aphid hosts. We also present data suggesting that the rates of
nonsynonymous substitutions are significantly higher in the endosymbiont
lineages than in the closely related free-living bacteria Escherichia coli
and Salmonella typhimurium. Synonymous substitution rates for Buchnera
approximate estimated mutation rates for E. coli and S. typhimurium, as
expected if synonymous changes act as neutral mutations in Buchnera. We
relate the observed differences in substitution frequencies to the absence
of selective codon preferences in Buchnera and to the influence of Muller's
ratchet on small asexual populations.
相似文献
45.
46.
Expression, and temporal and spatial distribution of type I collagen were investigated in chicken satellite cell cultures during differentiation. There was no difference in the relative amounts of type I collagen after treatment with basic fibroblast growth factor (FGF), insulin-like growth factor-I (IGF-I), or transforming growth factor beta 1 (TGF-beta 1). However, myotube morphology was influenced by the presence of the growth factors. The temporal and spatial distribution of type I collagen was also modified. Control cultures maintained a predominant distribution of type I collagen surrounding the cellular area until approximately 48 h after the initiation of fusion whereas cultures with FGF or IGF-I maintained a cellular localization of type I collagen throughout the fusion process. TGF-beta 1 resulted in the early formation of an extracellular network of type I collagen preceding control cultures by approximately 24 h. These results suggest that type I collagen expression but not localization is independent of satellite cell proliferation and differentiation. 相似文献
47.
M Ozkan SG Desai Y Zhang DM Stevenson J Beane EA White ML Guerinot LR Lynd 《Journal of industrial microbiology & biotechnology》2001,27(5):275-280
Characteristics of 13 newly isolated thermophilic, anaerobic, and cellulolytic strains were compared with previously described
strains of Clostridium thermocellum: ATCC 27405 and JW20 (ATCC 31549). Colony morphology, antibiotic sensitivity, fermentation end-products, and cellulose degradation
were documented. All 13 strains were sensitive to erythromycin (5 μg/ml) and chloramphenicol (25 μg/ml), and all strains but
one were sensitive to kanamycin (20 μg/ml). Polymerase chain reaction (PCR) amplification using primers based on gene sequences
from C. thermocellum ATCC 27405 was successful for all 13 strains in the case of the hydrogenase gene and 11 strains in the case of phosphotransacetylase/acetate
kinase genes. Ten strains amplified a product of the expected size with primers developed to be specific for C. thermocellum 16SrRNA primers. Two of the 13 strains did not amplify any product with the PCR primers designed for the phosphotransacetylase/acetate
kinase and 16SrRNA primers. A MboI-like GATC- recognizing restriction activity was present in all of the five strains examined. The results of this study have
several positive implications with respect to future development of a transformation system for cellulolytic thermophiles.
Journal of Industrial Microbiology & Biotechnology (2001) 27, 275–280.
Received 12 September 2000/ Accepted in revised form 20 November 2000 相似文献
48.
Syndecan-4 is a cell membrane heparan sulfate proteoglycan that is composed of a core protein and covalently attached glycosaminoglycans (GAG) and N-linked glycosylated (N-glycosylated) chains. Syndecan-4 has been shown to function independent of its GAG chains. Syndecan-4 may derive its biological function from the N-glycosylated chains due to the biological role of N-glycosylated chains in protein folding and cell membrane localization. The objective of the current study was to investigate the role of syndecan-4 N-glycosylated chains and the interaction between GAG and N-glycosylated chains in turkey myogenic satellite cell proliferation, differentiation, and fibroblast growth factor 2 (FGF2) responsiveness. The wild type turkey syndecan-4 and the syndecan-4 without GAG chains were cloned into the expression vector pCMS-EGFP and used as templates to generate syndecan-4 N-glycosylated one-chain and no-chain mutants with or without GAG chains. The wild type syndecan-4, all of the syndecan-4 N-glycosylated chain mutants were transfected into turkey myogenic satellite cells. Cell proliferation, differentiation, and responsiveness to FGF2 were measured. The overexpression of syndecan-4 N-glycosylated mutants with or without GAG chains did not change cell proliferation, differentiation, and responsiveness to FGF2 compared to the wild type syndecan-4 except that the overexpression of syndecan-4 N-glycosylated mutants without GAG chains increased cell proliferation at 48 and 72 h post-transfection. These data suggest that syndecan-4 functions in an FGF2-independent manner, and the N-glycosylated and GAG chains are required for syndecan-4 to regulate turkey myogenic satellite cell proliferation, but not differentiation. 相似文献
49.
50.
Syndecan-4 (S4) is a cell membrane heparan sulfate proteoglycan that plays a role in satellite cell mediated myogenesis. S4 modulates the proliferation of myogenic satellite cells, but the mechanism of how S4 functions during myogenesis is not well understood. In other cell systems, S4 has been shown to form oligomers in the cell membrane and interact through its cytoplasmic domain with the cytoskeletal protein α-actinin. This study addressed if S4 forms oligomers and interacts with α-actinin in muscle. The S4 cytoplasmic domain was found to interact with α-actinin in a phosphatidylinositol-4,5-bisphosphate dependent manner, but did not associate with vinculin. Through confocal microscopy, both S4 and syndecan-4 without the cytoplasmic domain were localized to the cell membrane. Although the cytoplasmic domain was necessary for the interaction with α-actinin, S4 oligomer formation occurred in the absence of the cytoplasmic domain. These data indicated that S4 function in skeletal muscle is mediated through the formation of oligomers and interaction with the cytoskeletal protein α-actinin. 相似文献