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51.
The role of the molybdenum cofactor (Mo cofactor) in the translocationof dimethyl sulfoxide (DMSO) reductase to the periplasmic spacewas studied in vivo by isolating chlorate-resistant mutantsof Rhodobacter sphaeroides f. sp. denitrificans. More than 50%of the chlorate-resistant mutants isolated were defective inthe biosynthesis of the Mo cofactor and all of these mutantsaccumulated the precursor form of the enzyme. About 45% of themutants contained the same level of Mo cofactor as the parentstrain and exhibited normal levels of DMSO reductase and nitratereductase activities when chlorate was absent from the medium,but the activities of these enzymes were depressed when chloratewas present. Much of the accumulated precursor form of the enzymein a Mo cofactor-deficient mutant was bound to the cytoplasmicmembrane and was sensitive to treatment with proteinase K fromthe periplasmic side of the membrane, an indication that theprecursor was exposed on the periplasmic surface of the membrane.The precursor accumulated on the membrane of the parent strainwhen molybdate was removed from the medium or upon additionof tungstate and this precursor was also sensitive to the treatmentwith proteinase K from the periplasmic side. These results suggestthat the Mo cofactor is necessary for proteolytic processingof the precursor to the mature enzyme on the periplasmic sideof the membrane, whereas binding of the precursor to the membraneand translocation across it can occur in the absence of thecofactor. Almost all of the Mo cofactor available for directreconstitution in vitro of nitrate reductase activity from thenit-l mutant of Neurospora crassa was present in the cytoplasmicfractions. (Received December 11, 1991; Accepted March 25, 1992) 相似文献
52.
Rice (Oryza sativa L. cv. Yamabiko) seedlings germinated underwater for 5 days contained small amounts of heme a and protohemebut no protochlorophyll(ide) [Pchl(ide)]. Levels of hemes andPchl(ide) increased rapidly upon transfer to air. When expressedin terms of fresh weight of tissue, hemes reached the levelsin aerobic controls after 24 h of contact with air, but Pchl(ide)did not. A comparison of the increases during 24-h adaptationto air in levels of heme a and Pchl(ide), which are specificto mitochondria and plastids, respectively, suggested that thedevelopment of mitochondria preceded that of plastids. The rateof synthesis of 5-aminolevulinic acid (ALA) was low in submergedseedlings, as compared to the rate in aerobic controls, butit increased during air adaptation. The sum of the amounts ofheme a, protoheme and Pchl(ide) increased in parallel with theamount of porphyrins, equivalent to the amount of ALA synthesizedduring the experimental period. When submerged seedlings thathad been pretreated with levulinic acid were exposed to air,no Pchl(ide) was formed. In contrast, Pchl(ide) accumulatedunder water when submerged seedlings were fed with ALA. Theseresults indicate that the synthesis of ALA, the limiting stepin the synthesis of Pchl(ide), is repressed under hypoxic conditions.
1 Present address: KRI International, Inc., Kyoto Research Park17, Chudoji Minami-machi, Shimogyo-ku, Kyoto, 600 Japan.
2 Present address: Research Institute for Bioresources, OkayamaUniversity, Kurashiki, 710 Japan. 相似文献
53.
Photo-induced activation of cytochrome P450/reductase fusion enzyme coupled with spinach chloroplasts 总被引:1,自引:0,他引:1
Young-Sug Kim Masayuki Hara Kazunori Ikebukuro Jun Miyake Hideo Ohkawa Isao Karube 《Biotechnology Techniques》1996,10(10):717-720
Summary Photoactivation of cytochrome P450 monooxygenase was studied using a combination of spinach chloroplasts and yeast microsomes containing rat P4501A1/yeast reductase fusion enzyme. Under illumination, in the reaction mixture, NADP was reduced, transferring electrons to the P450/reductase fusion enzyme to convert 7-ethoxycoumarin to 7-hydroxycoumarin. 相似文献
54.
Expression of gicerin in development, oncogenesis and regeneration of the chick kidney 总被引:1,自引:0,他引:1
55.
Maurizio Pellecchia Gerhard Wider Hideo Iwai Kurt Wüthrich 《Journal of biomolecular NMR》1997,10(2):193-197
A novel 2D NMR experiment, 2D HE(NE)HGHH, is presented for the assignment ofarginine side chain 1H and 15N resonances inuniformly 15N-labeled proteins. Correlations between1H, 1Hand 1H are established on the basis of3J(15N,1H) heteronuclear scalarcoupling constants, and sequence-specific assignments are obtained by overlapof these fragments with 1H chemical shiftsobtained by assignment procedures starting from the polypeptide backbone.Since guanidino protons exchange quite rapidly with the bulk water, the 2DHE(NE)HGHH pulse scheme has been optimized to avoid saturation and dephasingof the water magnetization during the course of the experiment. As anillustration, arginine side chain assignments are presented for two uniformly15N-labeled proteins of 7 and 23 kDa molecular weight. 相似文献
56.
The ratio of hapten and bovine serum albumin in an antigen conjugate was determined by matrix-assisted laser desorption/ionization mass spectrometry. A hybridoma secreting monoclonal antibodies against solamargine was produced by fusing splenocytes immunized with a solamargine-bovine serum albumin conjugate with HAT-sensitive mouse myeloma cell line, P3-X63-Ag8-653. Extensive cross-reaction of anti-solamargine antibodies against solasonine appeared. Aglycone of solamargine, solasodine cross-reacted with anti-solamargine antibodies resulting in a 43.8% cross-reaction. Insignificant cross-reaction appeared with tomatine (2.06%). The full measuring range of the assay extends from 57.5 pmol ml–1 to 11.5 nmol ml–1 of solamargine. 相似文献
57.
58.
In vivo and in vitro studies on the appearance of LHRH neurons in the hypothalamus of perinatal rats
Prof. Shigeo Daikoku Hitoshi Kawano Hideo Matsumura Shiro Saito 《Cell and tissue research》1978,194(3):433-445
Summary Ontogenetic development of LHRH-containing neurons was studied by fluorescence and enzyme immunohistochemistry in rats. In in vitro studies, the tissues of the septal-chiasmatic and mediobasal hypothalamic areas of fetal rats on day 16.5 or 18.5 of gestation were trypsinized separately for dissociation of the neural cells, and cultured for several days. Immunopositive reaction against LHRH was first detected in nerve cells derived from both areas of the hypothalamus of the fetuses on days 16.5 and 18.5 of gestation, after 8 and 6 days culture, respectively. The cells were small, and seemed to be bipolar in morphology indicating an axon and arborized dendrites. Immunopositive material occurred in the cell soma as well as in the cellular processes. In in vivo studies, immunopositive material, possibly deposited in nerve fibers, appeared first in OVLT and simultaneously in the external layer of the median eminence of fetuses on day 20.5 of gestation. The immunoreactive fibers increased in number in both parts with development, especially after birth in the median eminence. No immunopositive material was detected within any neural cell bodies nor in the cytoplasm of any ependymal cells.This work was financed by the Ministry of Education, Japan. No. 257008. We would like to thank Dr. Katsuhiko Saito (Department of Surgery, Tokushima University) for his kind advice on the preparation of the antibody used for the immunofluorescence study. 相似文献
59.
60.
Total phospholipids were extracted from cells of temperature sensitive unsaturated fatty acid auxotrophs of Escherichia coli (K-12 UFAts) grown at 28°C (PL28), and at 42°C in the presence of 2% KCl as an osmotic stabilizer (PL42 (KCl)). From the analysis of fatty acids, it was shown that the content of unsaturated fatty acids of PL42 (KCl) is only 9% of the total fatty acids, while that of PL28 is 54%. The thermal phase transitions of the bilayers prepared from the phospholipid fractions were studied by proton magnetic resonance. The line widths of the methylene signals and the sums of the methylene and methyl signal intensities were plotted against reciprocal values of absolute temperature 1/T or temperature itself. From the plots phase transitions were detected at about 19°C for PL28 and at 43°C for PL42 (KCl). In spite of its complex composition of fatty acids a highly cooperative transition was observed in the case of PL42 (KCl). It was also suggested that the phospholipids bilayers in the biomembranes of this strain at the growth temperature (42°C) are in the state where the gel and liquid crystalline phases coexist. 相似文献