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91.
Mitochondrial coupling factor-6 (CF-6) is a component of the ATP synthase complex essential for energy transduction. CF-6, which is localized to the surface of endothelial cells (ECs) and released by shear stress, has been implicated as an endogenous vasoconstrictor. Previous methods of obtaining CF-6 through purification and recombinant methods were laborious and inefficient. Here, we describe the chemical synthesis of human CF-6, (33-108)-NH(2), its C-terminal fragment (55-108)-NH(2), which is termed pCF-6; the rat CF-6, (33-108)-NH(2), its C-terminal fragment pCF-6, (55-108)-NH(2); and two N-terminal fragments of the rat pro-coupling factor-6, (24-52)-NH(2) and (33-52)-NH(2). Biological activities of each peptide were initially screened with bioassays and verified by in vivo studies. Accordingly, intravenous administration of CF-6, pCF-6, rat CF-6, and rat pCF-6 produced a modest but statistically significant increase in blood pressure and heart rate in urethane anesthetized rats, whereas the N-terminal rat pro-coupling factor-6, (24-52)-NH(2) and (33-52)-NH(2) caused no significant pressor response. Thus, the biologically active site probably resides at the C-terminal portion of CF-6 peptides. 相似文献
92.
Ouyang X Gulliford T Zhang H Smith G Huang G Epstein RJ 《Molecular and cellular biochemistry》2001,218(1-2):47-54
The carboxyterminal domain of the epidermal growth factor receptor (EGFR) – a putative binding site for the ubiquitin ligase Cbl – is the site of serine phosphorylation events which are essential for ligand-dependent EGFR desensitization and degradation. Using a monoclonal antibody (aPS1113) which selectively recognizes the homologous phosphorylated domain in the ErbB2 oncoprotein, we show here that wild-type ErbB2 becomes Ser1113-phosphorylated following treatment of 3T3 cells with growth factors or tyrosine phosphatase inhibitors. In EGFR-overexpressing A431 cells, ligand-inducible aPS1113 immunoreactivity declines more rapidly than other detectable phosphorylation events and is followed by EGFR downregulation. Analysis of 65 ErbB2-expressing primary breast cancers reveals a highly significant relationship between Ser1113 phosphorylation and EGFR overexpression (p < 0.0001) as well as an association with poor prognosis (p = 0.005). We submit that ErbB2 Ser1113 phosphorylation status represents a novel and informative biomarker of cancer cell biology and tumor behavior. 相似文献
93.
当归对高脂血清所致ECV304细胞损伤的保护作用 总被引:10,自引:0,他引:10
实验观察了高脂血清对培养的人脐静脉内皮细胞(ECV304)的损伤及传统中药当归的保护作用,以探讨当归的抗动脉粥样硬化作用及其可能机制,培养人脐静脉内皮细胞,以高脂血清作损伤因子,用扫描电镜观察细胞的超微结构,分光光度法检测细胞培养液中一氧化氮(NO)的含量,免疫细胞化学方法检测细胞表面细胞间粘附分子-1(ICAM-1),碱性成纤维细胞生长因子(bFGF)及转化生长因子β1(TGFβ)的表达,与高脂血清孵育24h后,内皮细胞的超微结构明显收损,且细胞表面ICAM-1,bFGF的表达明显增加,而细胞培养液中NO的量及细胞表达TGFβ1明显减少,加入当归后,高脂血清对内皮细胞的这些作用均可被逆转,当归对内皮细胞中ICAM-1,bFGF,TGFβ及NO表达改变的影响可能与其抗动脉粥样硬化的作用有关。 相似文献
94.
The phytohormone indole-3-acetic acid (IAA) plays a vital role in plant growth and development as a regulator of numerous biological processes. Its biosynthetic pathways have been studied for decades. Recent genetic and in vitro labeling evidence indicates that IAA in Arabidopsis thaliana and other plants is primarily synthesized from a precursor that is an intermediate in the tryptophan (Trp) biosynthetic pathway. To determine which intermediate(s) acts as the possible branchpoint for the Trp-independent IAA biosynthesis in plants, we took an in vivo approach by generating antisense indole-3-glycerol phosphate synthase (IGS) RNA transgenic plants and using available Arabidopsis Trp biosynthetic pathway mutants trp2-1 and trp3-1. Antisense transgenic plants display some auxin deficient-like phenotypes including small rosettes and reduced fertility. Protein gel blot analysis indicated that IGS expression was greatly reduced in the antisense lines. Quantitative analyses of IAA and Trp content in antisense IGS transgenic plants and Trp biosynthetic mutants revealed striking differences. Compared with wild-type plants, the Trp content in all the transgenic and mutant plants decreased significantly. However, total IAA levels were significantly decreased in antisense IGS transgenic plants, but remarkably increased in trp3-1 and trp2-1 plants. These results suggest that indole-3-glycerol phosphate (IGP) in the Arabidopsis Trp biosynthetic pathway serves as a branchpoint compound in the Trp-independent IAA de novo biosynthetic pathway. 相似文献
95.
Volkmann N Hanein D Ouyang G Trybus KM DeRosier DJ Lowey S 《Nature structural biology》2000,7(12):1147-1155
Structural insights into the interaction of smooth muscle myosin with actin have been provided by computer-based fitting of crystal structures into three-dimensional reconstructions obtained by electron cryomicroscopy, and by mapping of structural and dynamic changes in the actomyosin complex. The actomyosin structures determined in the presence and absence of MgADP differ significantly from each other, and from all crystallographic structures of unbound myosin. Coupled to a complex movement ( approximately 34 A) of the light chain binding domain upon MgADP release, we observed a approximately 9 degrees rotation of the myosin motor domain relative to the actin filament, and a closure of the cleft that divides the actin binding region of the myosin head. Cleft closure is achieved by a movement of the upper 50 kDa region, while parts of the lower 50 kDa region are stabilized through strong interactions with actin. This model supports a mechanism in which binding of MgATP at the active site opens the cleft and disrupts the interface, thereby releasing myosin from actin. 相似文献
96.
To relieve lactic acid inhibition, an aqueous two-phase system (ATPS) was used to grow Lactococcus lactis. Its composition was 11% (w/v) PEG 20000/3.5% (w/v) MgSO4 7H2O. In this ATPS medium, the cells were completely partitioned in the bottom phase, and lactic acid had the biggest partition coefficient of the eight ATPS media tested. The cell biomass in this medium was 0.64 mg ml–1, only 60% of that of the control medium, but nisin production (803 IU ml–1) was enhanced by 33%. The increase in nisin was explained as a result of extraction of lactic acid from the bottom phase to the top one. The changes of tie-line length and phase volume ratio for the identical tie line could affect cell growth and nisin accumulation. 相似文献
97.
Plant regeneration through organogenesis from callus induced from mature zygotic embryos of loblolly pine 总被引:8,自引:1,他引:7
Mature zygotic embryos from three seed sources of loblolly pine were cultured on callus induction medium containing 10 mg
l–1
α-naphthaleneacetic acid, 4 mg l–1 benzyladenine (BA), 400 mg l–1 casein hydrolysate, and 400 mg l–1 glutamine for 6 weeks. Light-yellow, loose, glossy, globular callus was formed, and the highest frequency was 35.7%. The
highest differentiation frequency of callus on adventitious bud induction medium was 62.1%. After culture of calli with adventitious
buds on elongation medium for 6 weeks, adventitious shoots more than 1.0 cm in height were selected for rooting. On rooting
medium supplemented with 0.1 mg l–1 indole-3-butyric acid, 1 mg l–1 BA, and 0.5 mg l–1 gibberellic acid, the highest rooting frequency of adventitious shoots was 46% in a culture period of 6 weeks. Established
plants survived following transfer to soil at a frequency of 71%.
Received: 14 May 1997 / Revision received: 25 September 1997 / Accepted: 11 October 1997 相似文献
98.
Propagation of potato tubers in a nutrient mist bioreactor 总被引:1,自引:0,他引:1
Zhenlong Hao Fan Ouyang Yuxuan Geng Xiangdong Deng Zanmin Hu Zhenghua Chen 《Biotechnology Techniques》1998,12(8):641-644
The newly designed nutrient mist bioreactor provided an environment supporting multiple-layer culture. In vitro tubers of potato (Solanum tuberosum L.) were induced and cultured in this bioreactor by using two culture methods. The percentage of the inocula eventually forming tubers in a two-step method was 98% with only 54% being formed in a one-step method. The two-step method improved the efficiency of tuber induction, expedited and synchronized the tuberization. © Rapid Science Ltd. 1998 相似文献
99.
Metal ion binding to calmodulin: NMR and fluorescence studies 总被引:13,自引:0,他引:13
Calmodulin is an important second messenger protein which is involved in a large variety of cellular path-ways.Calmodulin is sensitive to fluctuations in the intracellular Ca levels and is activated by the bindingof four Ca ions. In spite of the important role it plays in signal transduction pathways, it shows a surpris-inglybroad specificity for binding metal ions. Using 15N-Gly biosynthetically-labelled calmodulin, we havestudied the binding of different metal ions to calmodulin, including K+, Na+, Ca, Mg, Zn, Cd, Pb, Hg, Sr, La and Lu, by 1H, 15N HMQC NMR experiments. The effects of these ions on the substrate-bindingability of calmodulin have also been studied by fluorescence spectroscopy of the single tryptophan residue in a 22-residue synthetic peptide encompassing the skeletal muscle myosin light chain kinase calmod-ulin-binding domain. Most of these metal ions can activate a calmodulin target enzyme to some extent,though they bind to calmodulin in a different manner. Mg, which is of direct physiological interest, has adistinct site-preference for calmodulin, as it shows the highest affinity for site I in the N-terminal domain,while the C-terminal sites III and IV are the high affinity binding sites for Ca (as well as for Cd ). At ahigh concentration of Mg and a low concentration of Ca, calmodulin can bind Mg in its N-terminallobe while the C-terminal domain is occupied by Ca; this species could exist in resting cells in which the Mg level significantly exceeds that of Ca. Moreover, our data suggest that the toxicity of Pb-which,like Sr, binds with an equal and high affinity to all four sites-may be related to its capacity to tightlybind and improperly activate calmodulin. 相似文献
100.
耐菊(Steviarebaudiana)愈伤组织中甜菊糖苷的积累与愈伤组织的生长呈负相关、与愈伤组织细胞的组织化及转绿呈正相关。愈伤组织芽的分化并不是积累较高水平甜菊糖苷的必要前提。绿色、质地致密、生长缓慢的愈伤组织,不论有芽分化或无芽分化时,其甜菊糖苷含量均较高。在电镜下观察到,这两种愈伤组织细胞具有类似的超微结构特征:细胞高度液泡化;叶绿体发育成熟,光合膜系统结构发达,基质浓厚且含有质体小球;微体具有典型的晶格结构,常与叶绿体紧密相靠。黄色、质地致密、生长缓慢的愈伤组织中甜菊糖苷含量较低,其细胞内质体富含淀粉粒,只有少量分散的片层结构,有的质体甚至完全被淀粉粒所充塞。黄色、质地疏松、生长快速的愈伤组织中甜菊糖苷含量最低,其细胞内质体结构简单,片层稀少。质体的发育和液泡的分化与甜菊糖苷的积累密切相关。愈伤组织具有较高的甜菊糖苷含量在于愈伤组织细胞的组织化以及细胞的高度液泡化并具有发育成熟的叶绿体。 相似文献