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51.
Effect of mutations at Met-88 and Met-90 on the biotination of Lys-89 of the apo 1.3S subunit of transcarboxylase 总被引:3,自引:0,他引:3
The apo 1.3S subunit of transcarboxylase contains the sequence Ala-87-Met-88-Lys-89-Met-90, and it is Lys-89 that is biotinated. This sequence is highly conserved in all the biotin enzymes that have been sequenced (with the exception of acetyl-CoA carboxylase from chicken liver, which has Val in place of Ala). The role of Met-88 and Met-90 in specifying Lys-89 for biotination by synthetase was examined by site-directed mutagenesis. Genes of the 1.3S subunit coding for Thr-88, Leu-88, or Leu-90 were generated by oligonucleotide-directed in vitro mutagenesis and expressed in Escherichia coli. The mutated apo 1.3S subunits were isolated and the biotination by homogeneous synthetase from Propionibacterium shermanii was compared with that of the apo wild-type subunit. The Vmax for the apo mutants was the same as that for the apo wild type, but when Leu was substituted for Met-88 or Met-90, the Km for the mutant was lower than that of the wild-type or mutant Thr-88. The activity of the synthetase of E. coli was determined by an in vivo assay. During the early log phase of growth, a smaller portion of mutants Thr-88 and Leu-90 was biotinated than with the wild-type or mutant Leu-88. When the cultures progressed to stationary phase, mutants and the wild type were biotinated to the same extent. The overall results show that Met-88 and Met-90 are not required for biotination of the apo 1.3S subunit by the synthetases. 相似文献
52.
J Murray-Rust A N McLeod T L Blundell S P Wood 《BioEssays : news and reviews in molecular, cellular and developmental biology》1992,14(5):325-331
Insulin is a member of a family of hormones, growth factors and neuropeptides which are found in both vertebrates and invertebrates. A common 'insulin fold' is probably adopted by all family members. Although the specificities of receptor binding are different, there is a possibility of co-evolution of polypeptides and their receptors. 相似文献
53.
A single beta-globin locus control region element (5'' hypersensitive site 2) is sufficient for developmental regulation of human globin genes in transgenic mice. 总被引:3,自引:0,他引:3 下载免费PDF全文
B J Morley C A Abbott J A Sharpe J Lida P S Chan-Thomas W G Wood 《Molecular and cellular biology》1992,12(5):2057-2066
54.
Isolated primary follicles from 10-day-old mice were cultured in a collagen gel matrix for 6 days in Minimum Essential Medium + foetal calf serum, followed by culture in unsupplemented medium (control) or in medium containing hypoxanthine (2 mM) or dibutyryl cyclic adenosine monophosphate (dbcAMP, 0.25 mM) for a further 3 or 6 days. Less than 10% of oocytes resumed meiosis during the culture period in all groups. At recovery, the diameter of oocytes at the germinal vesicle stage was recorded and their ability to resume meiosis was determined. Hypoxanthine had little effect on oocyte growth and meiotic competence, but culture in dbcAMP resulted in oocytes that were larger (60.2 +/- 0.6 microns) than those of controls (55.8 +/- 0.5 microns) and more competent to resume meiosis than were controls (42.9% and 10.8%, respectively). The addition of dbcAMP to the culture medium induced a 4-5-fold increase in the number of granulosa cells oocyte compared with controls (3757 +/- 423 and 838 +/- 93, respectively). These results indicate that increased oocyte growth and meiotic competence is primarily mediated via dbcAMP effects on the granulosa cells. 相似文献
55.
J C Wood J A Copland T G Muldoon L B Hendry 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1991,197(4):404-408
3-Phenylacetylamino-2,6-piperidinedione (A10), an amino acid analog, has been reported to possess antineoplastic activity against certain neoplastic tissues. The antimitogenic properties of A10 were studied by determining its effect on prolactin (PRL)- and interleukin 2 (IL-2)-stimulated mitogenic responses in the rat Nb2 lymphoma cell line. The addition of A10 (1-12 mM) to PRL (0.4 ng/ml)-stimulated cells inhibited growth in a dose-dependent manner. DNA synthesis patterns studied by thymidine incorporation demonstrated that A10 was significantly inhibitory (25% at 20 hr; 50% at 40 hr, P less than 0.01). IL-2 stimulation of mitogenesis was also sensitive to A10 inhibition. The inhibition of PRL stimulated mitogenesis was reversible when A10 was removed after 24 hr of culture and A10 showed no toxicity in a chromium release assay. These data suggest that A10 effects may be cytostatic, rather than cytotoxic. 相似文献
56.
Do plasma ACTH and cortisol concentrations in the late-gestation fetal sheep vary diurnally? 总被引:1,自引:0,他引:1
This study tested the hypothesis that fetal plasma ACTH and cortisol concentrations vary diurnally, and the mean concentration and the amplitude of the rhythm vary as a function of fetal gestational age. Nine chronically-catheterized fetal sheep were studied between 120 and 142 days' gestation. All of the fetuses were born spontaneously and alive. The pregnant ewes were maintained in a room with a regular light cycle (on at 07.30, off at 17.30). Food and water were available ad libitum. Blood samples were drawn at 4-h intervals throughout a 24-h period. There were no significant daily variations in fetal plasma ACTH, cortisol, or progesterone concentrations, except in the last 3 days of fetal life. In these fetuses ACTH and cortisol concentrations were increased in the afternoon and evening. We conclude that there is no diurnal rhythm in ovine fetal hypothalamo-pituitary-adrenal axis activity, and that the increased plasma concentrations of ACTH and cortisol in the afternoon and evening hours of the last few days of fetal life might be a response to increased uterine contraction activity. 相似文献
57.
58.
The GTPase stimulatory activities of the neurofibromatosis type 1 and the yeast IRA2 proteins are inhibited by arachidonic acid. 总被引:3,自引:1,他引:2 下载免费PDF全文
M Golubi K Tanaka S Dobrowolski D Wood M H Tsai M Marshall F Tamanoi D W Stacey 《The EMBO journal》1991,10(10):2897-2903
Three proteins, GTPase activating protein (GAP), neurofibromatosis 1 (NF1) and the yeast inhibitory regulator of the RAS-cAMP pathway (IRA2), have the ability to stimulate the GTPase activity of Ras proteins from higher animals or yeast. Previous studies indicate that certain lipids are able to inhibit this activity associated with the mammalian GAP protein. Inhibition of GAP would be expected to biologically activate Ras protein. In these studies arachidonic acid is shown also to inhibit the activity of the catalytic fragments of the other two proteins, mammalian NF1 and the yeast IRA2 proteins. In addition, phosphatidic acid (containing arachidonic and stearic acid) was inhibitory for the catalytic fragment of NF1 protein, but did not inhibit the catalytic fragments of GAP or IRA2 proteins. These observations emphasize the biochemical similarity of these proteins and provide support for the suggestion that lipids might play an important role in their biological control, and therefore also in the control of Ras activity and cellular proliferation. 相似文献
59.
Prohibitin, an evolutionarily conserved intracellular protein that blocks DNA synthesis in normal fibroblasts and HeLa cells. 总被引:21,自引:7,他引:14
M J Nuell D A Stewart L Walker V Friedman C M Wood G A Owens J R Smith E L Schneider R Dell' Orco C K Lumpkin et al. 《Molecular and cellular biology》1991,11(3):1372-1381
Genes that act inside the cell to negatively regulate proliferation are of great interest because of their implications for such processes as development and cancer, but these genes have been difficult to clone. This report details the cloning and analysis of cDNA for prohibitin, a novel mammalian antiproliferative protein. Microinjection of synthetic prohibitin mRNA blocks entry into S phase in both normal fibroblasts and HeLa cells. Microinjection of an antisense oligonucleotide stimulates entry into S phase. By sequence comparison, the prohibitin gene appears to be the mammalian analog of Cc, a Drosophila gene that is vital for normal development. 相似文献
60.
Cytoskeletal proteins in adherens-type cell-matrix junctions. 总被引:1,自引:0,他引:1
D R Critchley A Gilmore L Hemmings P Jackson A McGregor V Ohanian B Patel G Waites C Wood 《Biochemical Society transactions》1991,19(4):1028-1033