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41.
Our previous study indicated that nuclear protein factors of HeLa cells specifically bind to three nuclear Mt elements, Mt1, Mt3, and Mt4, located in the 5'-flanking regions of the human nuclear genes for cytochrome c1 and for ubiquinone-binding protein, both of which are subunits of mitochondrial cytochrome bc1 complex (Suzuki, H., Hosokawa, Y., Toda, H., Nishikimi, M., and Ozawa, T. (1990) J. Biol. Chem. 265, 8159-8163). In this study, we examined whether the same nuclear factors could recognize a set of the Mt3 and Mt4 elements that were found in the displacement loop and the promoter region of mammalian mitochondrial genomes. Gel retardation experiments disclosed that the same nuclear protein factors specifically bind to those Mt elements in the human mitochondrial genome as well as to the nuclear Mt3 and Mt4 elements of the two genes, and that the coexistence of both the elements is required for the efficient binding. The nuclear protein factors which recognize the Mt elements located in the regulatory regions of the nuclear and mitochondrial genes may play an important role in coordinate expression of the two physically separated genes during mitochondrial biogenesis. 相似文献
42.
Glycoprotein-binding site of dystrophin is confined to the cysteine-rich domain and the first half of the carboxy-terminal domain. 总被引:10,自引:0,他引:10
Dystrophin, a protein product of the Duchenne muscular dystrophy gene, is thought to associate with the muscle membrane by way of a glycoprotein complex which was co-purified with dystrophin. Here, we firstly demonstrate direct biochemical evidence for association of the carboxy-terminal region of dystrophin with the glycoprotein complex. The binding site is found to lie further inward than previously expected and confined to the cysteine-rich domain and the first half of the carboxy-terminal domain. Since this portion corresponds well to the region that, when missing, results in severe phenotypes, our finding may provide a molecular basis of the disease. 相似文献
43.
A Yoshimura C Fujitsuka K Kawakami N Ozawa H Ojala N Fujitsuka 《Journal of applied physiology》1992,73(5):1925-1931
With the use of myosin adenosinetriphosphatase (ATPase) and immunofluorescence staining methods, the adaptive responses of intrafusal and extrafusal fibers to endurance swimming were studied in frozen sections of rat soleus (SOL) and extensor digitorum longus (EDL) muscles. Glycogen depletion confirmed muscle fatigue at the end of a standardized bout of exercise. No significant age-dependent changes in myosin isoforms were detected in any fibers. The 12-wk training increased type I fibers by 10.9% in the SOL and type IIa fibers in the EDL by 16.6%. In trained muscle sections, both staining methods identified a permuted chain fiber, expressed the same as the myosin isoform in the bag2 fiber. However, no exercise-induced change of myosin isoform profile was found in the bag1 and bag2 fibers. Myosin ATPase (and immunofluorescence) staining showed the percentage of permuted chain fibers increased from 0 to 6.7% (5.6%) after 6 wk of training and to 19.2% (14.1%) after 12 wk of training and that it was still at 6.1% (4.2%) 10 wks after training. A novel myosin isoform may thus be expressed in nuclear chain fibers by repetitive recruitment of muscle spindles. 相似文献
44.
S Nagao S Matsuki H Kanoh T Ozawa K Yamada Y Nozawa 《The Journal of biological chemistry》1990,265(11):5926-5929
Tetrahymena calmodulin (CaM) differs from mammalian CaM in its ability to activate Tetrahymena guanylate cyclase. Of 12 differences in amino acid sequence, two occur near the carboxyl terminus (Gln-143----Arg and Thr-146----deletion). To investigate the functional significance of the carboxyl-terminal region in activation of the guanylate cyclase, three mutated CaMs were engineered by using cassette mutagenesis of rat CaM cDNA: Gln-143----Arg (CaM.A), Thr-146----deletion (CaM.D), and Gln-143----Arg/Thr-146 deletion (CaM.AD). Recombinant wild type CaM (wCaM), CaM.A, CaM.D, and CaM.AD were indistinguishable in their ability to activate cyclic AMP phosphodiesterase. The two mutated CaMs (CaM.A and CaM.AD) with the Gln-143 replacement activated guanylate cyclase of Tetrahymena plasma membrane in the presence of Ca2+, with the maximal activation being half of that produced by Tetrahymena CaM. In contrast, neither CaM.D nor wCaM could stimulate the cyclase activity. A CaM antagonist, W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide), prevented the cyclase activation by either Tetrahymena CaM, CaM.A, or CaM.AD. Thus, we conclude that Arg-143 is in a region of the molecule involved in activation of Tetrahymena guanylate cyclase. The data also suggest that the cyclase activation by Tetrahymena CaM requires complex macromolecular interactions between the entire CaM molecule and the enzyme. 相似文献
45.
Kunie Yoshikawa Takehiko Nohmi Rumiko Miyata Motoi Ishidate Jr. Naoki Ozawa Masakazu Isobe Tadashi Watabe Tuneo Kada Takashi Kawachi 《Mutation research》1982,96(2-3)
Comparison studies for detecting differences between liver microsome and S9 preparations from 4 strains (Donryu, Fischer, Sprague-Dawley, Wistar) of young male rats were carried out with pretreatment of the animals by inducers such as PCBs and PB plus 5,6-BF. Each microsome fraction was assayed for the enzymic activity of metabolism of model substrates such as aniline, benzophetamine, BP, DMN and 7-ethoxycoumarin. The hepatic S9 sample was also compared, as regards its metabolizing ability to activate 9 pre-mutagens (2AA, AAF, o-AAT, BP, DAB, DMBA, DMN, m-PDA, quinoline) to directly acting mutagens in the Salmonella/hepatic S9 activation test by using TA98, TA100 and TA1537 strains with or without cytochrome P450 inhibitors (SKF-525A, metyrapone, 7,8-benzoflavone).In the enzymic assay with PCBs-induced microsomes, BP hydroxylation revealed a strain-specific difference: the microsomes from Fischer and Wistar rats were more effective for metabolizing BP than those from the other strains of rat. The effect of induction by PB plus 5,6-BF for Fischer rats showed relatively higher enzymic activity in the same induction group. Other microsomes prepared from rats with and without induction by PB plus 5,6-BF did not show a clear-cut strain dependency in the enzymic activities assayed.In the mutation experiments with hepatic S9 samples, the examination of DAB and quinoline revealed a marked strain difference when S9 samples prepared from PCBs-pretreated and PB-plus-5,6-BF-induced rats were used: the S9 sample from Fischer rats was available for activating the two pre-mutagens to directly acting mutagens. No marked difference in the metabolic activation of the remaining 7-pre-mutagens was observed on other S9 preparations.In examinations of mutagenicity activities with the use of three inhibitors, the two S9 preparations made with the two induction methods showed inhibition profiles closely similar to each other. However, there were minor differences in the profiles by these inhibitors.From these findings it was concluded that Fischer rat-liver S9 is useful for detecting mutagens in the metabolic activation test, when induction by PB plus 5,6-BF was used in the Ames Salmonella test. 相似文献
46.
Toshio Nakatani Kazue Ozawa Motokazu Asano Minoru Ukikusa Yasuo Kamiyama Takayoshi Tobe 《Life sciences》1981,28(3):257-264
The changes in the energy substrate utilized by the remnant liver were studied in relation to the changes in the cellular energy status of 25 and 70% hepatectomized rabbits. In 25% hepatectomized rabbits, the energy charge level of the remnant liver remained unchanged, the energy substrate of which was predominantly glucose, rather than fatty acid. In contrast, in 70% hepatectomized rabbits, the energy production by the mitochondria was mainly dependent upon fatty acid oxidation at the early period after hepatectomy when the energy charge level decreased remarkably, and then upon glucose oxidation, concomitant with the restoration of the energy charge. It is suggested that the changes in the energy substrate utilized are closely related to those in the energy charge level and the mitochondrial phosphorylative activity of the remnant liver following hepatectomy. 相似文献
47.
The preparation of cell fusion-inducing proteoliposomes from purified glycoproteins of HVJ (Sendai virus) and chemically defined lipids 总被引:1,自引:0,他引:1
Cell fusion-inducing (fusogenic) proteoliposomes of defined chemical composition were reconstituted from purified glycoproteins of hemagglutinating virus of Japan (Sendai virus) either with lipids extracted from the virus particles or with a chemically defined lipid mixture. Cell fusion reactions induced by the reconstituted system have several important characteristics similar to the virus-induced fusion reaction: fusogenic activity of the proteoliposomes depends on the presence of active fusion protein in the vesicles and, in the case of Ehrlich tumor cells, the fusion is almost completely inhibited by adding cytochalasin D to a final concentration of 4 microgram/ml. The only known difference between the original and reconstituted systems is that a greater amount of the latter is necessary for the same degree of fusogenic activity. Thus, the reconstituted system can be used as a model for the Sendai virus-induced fusion reaction. A lipid mixture (phosphatidylcholine:phosphatidylethanolamine:phosphatidylserine:sphingomyelin = 1:2:1:1, by weight, and cholesterol equimolar to the total phospholipids) similar to that of the virion was active for reconstitution, whereas a mixture containing the same composition of phospholipids but no cholesterol, and ones containing cholesterol with only a single species of phospholipid were not reconstitutively active. 相似文献
48.
49.
In order to examine the hypothesis that the thyroidal responsiveness to TSH is under the influence of thyroid hormone, following the T3 injection to the mice, serum T3 concentrations and the response of thyroid tissue to a fixed dose of TSH in terms of intracellular colloid droplet formation was studied. The colloid droplets induced by TSH was significantly reduced when serum T3 was decreasing, while it was significantly increased when serum T3 was increasing. This results demonstrate for the first time the existence of short feed-back loop regulating intra-thyroidal function by circulating T3. To delineate the possible mechanism of action of T3, the thyroid gland of mouse whose serum T3 concentration was elevated by injecting 50 mug T3, was incubated with TSH in vitro. TSH-induced cyclic AMP generation was not inhibited at all but colloid droplet formation was significantly inhibited in the thyroid tissue of the animal whose serum T3 concentration was enormously high. Thus, it was demonstrated that the site at which T3 affects is beyond cylcic AMP generation but prior to endocytosis, being consistent with our previous results. 相似文献
50.