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121.
The substrate specificity of phospholipid/Ca2+-dependent protein kinase (protein kinase C) was studied using synthetic peptides, in particular those corresponding to the amino acid sequence around serine 115 in bovine myelin basic protein (MBP). It was found that MBP (104-118) and MBP (104-123) were substrates for the enzyme, with apparent Km values of 14 and 10 microM, respectively. Neither MBP (111-118) nor MBP (111-123) were phosphorylated, indicating that an additional segment of sequence extending toward the N terminus, but not toward the C terminus, was essential for the substrate activity of the peptides. Of the alanine-substituted analogs examined, [Ala 105] MBP (104-118) was comparable to the parent peptide, whereas [Ala 107] MBP (104-118) and [Ala 113] MBP-(104-118) were much poorer substrates. These findings indicated that lysine 105 was not essential, but both arginine 107 and arginine 113 were important specificity determinants. Initial studies revealed that [Ala 113] MBP (104-118) inhibited phosphorylation by the enzyme of the parent peptide and, to a lesser extent, the intact MBP(1-170). Serine 115 was the only site phosphorylated in the analog peptides [Ala 105] MBP (104-118) and [Ala 107]MBP (104-118). In the parent peptide, serine 115 was the initial site of phosphorylation but after prolonged phosphorylation other sites became phosphorylated (serine 110 and/or serine 112), further supporting the concept that arginine residues act as essential substrate specificity determinants for phospholipid/Ca2+-dependent protein kinase. 相似文献
122.
Ren-Huan Tang Min-Min Su Tong-Geng Cao Yuan-Fang Liu 《Biological trace element research》1985,7(2):95-102
Using two Chinese strains ofTetrahymena pyriformis, S1 and BJ4, as the biological models, the effects of lighter rare earths (lanthanum, cerium, praseodymium, neodymium, samarium, and europium), representatives of heavier rare earths (yttrium and thulium), and mixed rare earths were studied. The stimulation of population growth ofTetrahymena in peptone-glucose media containing trace amounts of these elements have been observed. The mechanisms for the beneficial effects of rare earth elements in low concentrations remains to be discovered. 相似文献
123.
124.
Yasuyuki Kurihara Nobumoto Miyashita Kazuo Moriwaki Michael L. Petras François Bonhomme Wang Su Cho Sei-ichi Kohno 《Immunogenetics》1985,22(3):211-218
Allelic distributions of Thy-1, Ly-l, and Ly-2 antigens in wild mice are characteristic of each Mus musculus subspecies. Eastern mice (M.m.molossinus, M.mmusculus, M.m.castaneus, M.m.bactrianus) express the Thy-1.1 antigen, whereas Western mice (M.m. domesticus, M.m.brevirostris) express the Thy-1.2. All mice from wild populations examined in this survey express the Ly-1.2. The Ly-2.1 is distributed in Eastern mice and some Western mice, and the Ly-2.2 is found in the remaining Western mice. Allelic distributions of these antigens were also examined in two other species, Mus spretus and Mus spicilegus. Allelic constitutions of Thy-1 and Ly-1 in these species are similar to those of Eastern mice. Some M.spicilegus, however, express the Ly-1.1 antigen. This antigenic type is not found in M.musculus. Some Eastern mice related to M.m.castaneus react weakly to Ly-1.2-specific and Ly-2.1-specific monoclonal antibodies in both the complement-mediated cytotoxicity test and the absorption test. These results suggest that M.m.castaneus has unique alleles in the Ly-1 and Ly-2 loci. 相似文献
125.
Evidence is presented to indicate a metabolic relationship between arachidonic acid activation and its transfer to lysophospholipds by brain microsomes. Thus, in the presence of 1-acylglycerophosphocholines or 1-acyl-glycerophosphoinositols, the activation of labeled arachidonate to its acyl-CoA was enhanced, and the acyl-CoA formed was, in turn, transferred to the lysophospholipids to form the respective diacyl-glycerophospholipids. The coupling effect seems to pertain mainly to the lysophospholipids which are good substrates of the acyltransferase. Other lyso-compounds were either not effective or inhibitory to the arachidonate activation process. The activation-transfer activity mediated by the fatty acid ligase and acyltransferase could be dissociated by Triton X-100, which apparently stimulated the acyl-CoA ligase activity but inhibited the acyltransferase. These results suggest that fatty acid ligase and acyltransferase are located in close proximity within the membrane domain. The existence of a close metabolic relationship between these two enzymic reactions is important for maintaining a dynamic equilibrium between the free fatty acids and the membrane phospholipids. The mechanism is also useful in regulating the cellular acyl-CoA and lysophospholipid metabolism, because both compounds have membrane perturbing properties when present in excessive quantity. 相似文献
126.
127.
Papaya (Carica papaya L.) anther containing microspores in tetrad to early-binucleate stages were successfully cultured on 1/2 strength MS salts and vitamins with full strength Na-Fe-EDTA supplemented with 2 mg/l NAA, 1 mg/l BA and 6% sucrose for callus initiation and formation. Highest frequencies of callus induction were obtained when anthers at the uninucleate stage were cultured in the dark. Haploid plantlets and pollen-derived embryoids were obtained from anthers cultured at the uninucleate stage on solidified MS medium containing 3% sucrose without any growth regulators under a low light intensity (1,500 lux). Large quantities of embryoids were obtained when the original embryoids were transferred to MS medium with 3% sucrose and no growth regulators. Cytology of root tips of embryoid-derived plants confirmed the haploid chromosome number of 9 indicating that the embryoids originated from pollen.Abbreviations MS
Murashige and Skoog (1962)
- MAA
naphthaleneacetic acid
- BA
6-benzyladenine
- 2,4-D
2,4-dichlorophenoxyacetic acid 相似文献
128.
“同时蒸馏-萃取”分析茉莉花香成分 总被引:5,自引:0,他引:5
用一种经过改进的“同时蒸馏-萃取”仪提取了茉莉花的香成分,以 GC/MS 和 Kovats保留指数法鉴定了提取物中的28个化学成分。主要成分为:芳樟醇、乙酸苯甲酯、顺-石竹萜烯、榧烯醇、苯甲酸顺-3-己烯酯、邻氨基苯甲酸甲酯、二十三烯-11及吲哚。讨论了鲜花香成分和植物精油的采集与分析方法。 相似文献
129.
130.