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981.
Amino acid sequence homology between rat prostatic steroid binding protein and rabbit uteroglobin 总被引:2,自引:0,他引:2
M E Baker 《Biochemical and biophysical research communications》1983,114(1):325-330
Using a computer program designed to detect evolutionary relationships between proteins, I find that the polypeptide chain of rabbit uteroglobin has amino acid sequence homology with the C1 and C2 polypeptide chains of rat prostatic steroid binding protein. Using this finding I suggest several interesting approaches for studying the biology of these proteins. 相似文献
982.
Gideon Bach Elizabeth F. Neufeld 《Biochemical and biophysical research communications》1983,112(1):198-205
The biosynthesis of arylsulfatase A was studied in cultured fibroblasts by pulse-chase labeling with [2-3H]mannose; the enzyme was isolated by immunoprecipitation and denaturing polyacrylamide gel electrophoresis. In normal fibroblasts, and in fibroblasts from a patient with multiple sulfatase deficiency, the enzyme was synthesized as a glycoprotein of apparent molecular weight of 59,000; half of it was processed over a period of 4 days to Mr= 57,000. The precursor chain of Mr= 59,000 was secreted in the presence of 10 mM NH4Cl. An immunoprecipitable glycoprotein of normal size was synthesized by fibroblasts from two unrelated patients with metachromatic leukodystrophy, but this material disappeared within twenty hours. In fibroblasts from an individual with pseudodeficiency of arylsulfatase A, the immunoprecipitable precursor glycoprotein was smaller (Mr= 56,000). The synthesis of cross-reactive proteins with altered properties supports the concept of allelic mutations as the genetic basis of metachromatic leukodystrophy and of arylsulfatase A pseudodeficiency. 相似文献
983.
R Dante M Arnaud A Niveleau 《Biochemical and biophysical research communications》1983,114(1):214-221
The treatment of transformed rat cells with micromolar amounts of 5'deoxy 5'methyl thioadenosine induces rapid effects on the rate of methylation of DNA concomitantly with alterations of intracellular pools of S-adenosyl methionine and S-adenosyl homocysteine. Pulse chase labelling experiments indicate that 5'deoxy 5'methylthioadenosine does not inhibit the degradation of S-adenosyl homocysteine but inhibits the consumption of S-adenosyl methionine. In vitro transmethylation assays performed with heterologous DNA show that low doses of the thioethernucleoside do not significantly affect the DNA methyltransferase activity of cellular extracts. The biological role of 5'deoxy 5'methylthioadenosine, a natural molecule formed during the synthesis of polyamines is discussed. 相似文献
984.
The various diapause and post-diapause stages entered by cabbage root fly pupae during the overwintering period are shown schematically. Although diapause induction started in mid-Aug., the early-pupating insects did not develop further but were maintained in diapause by the warm autumn temperatures. Therefore, diapause development was simultaneous in all Wellesbourne pupae, whether of second or third generation origin. Diapause development started only in mid-Oct., when mean soil temperatures fell below 10°. In the field, 90% of the overwintering population of cabbage root fly pupae had completed pleted diapause by 5 March 1980, 17 Feb. 1981 and 18 Feb. 1982. This was equivalent to a duration of 19 weeks from mid-Oct. onwards, during the winters of 1979–80, 1980–81 and 1981–82 respectively. A further break between the completion of diapause and the warm conditions required to start post-diapause development also helps to condense the emergence of flies in the spring. Hence, an accurate forecast of the time of spring attack by populations of flies similar to those at Wellesbourne should be possible.This study was financed partly by the Commission of the European Communities as CEC Contract No. 0771. 相似文献
985.
Mitogenic response to epidermal growth factor (EGF) modulated by platelet-derived growth factor in cultured fibroblasts 总被引:1,自引:0,他引:1
Walker Wharton Edward Leof Nancy Olashaw E. J. O''Keefe W. J. Pledger 《Experimental cell research》1983,147(2):443-448
The mitotic effects of epidermal growth factor (EGF) were investigated in two cultured fibroblast lines, BALB/c-3T3 and C3H 10T1/2 cells. EGF (30 ng/ml) added to quiescent 3T3 cells in medium containing either platelet-poor plasma or 10(-5) M insulin caused only minimal increases in the percentage of cells stimulated to initiate DNA synthesis. In contrast, EGF acted synergistically with either insulin or plasma to stimulate DNA synthesis in quiescent cultures of 10T1/2 cells, although the maximum effects of EGF were measured at concentrations several-fold greater than those found in either serum or plasma. In either 3T3 or 10T1/2 cells a transient preexposure to platelet-derived growth factor (PDGF) caused over a 10-fold increase in the sensitivity to the mitogenic effects of EGF. It is therefore possible that a primary action of PDGF is to increase the sensitivity of fibroblasts to EGF, independent of whether EGF alone is found to be mitogenic. 相似文献
986.
Liposome-mediated labeling of adrenocorticotropin fragments parallels their biological activity 总被引:2,自引:0,他引:2
To test our hypothesis that specific interactions of ACTH peptides with model lipid membranes reflect the biological importance of similar interactions on target cells, we investigated the liposome-mediated labeling of ACTH fragments with the extremely hydrophobic photolabel, 3-trifluoromethyl-3-(m-[125I]iodophenyl)diazirine. Correlations were found between the labeling rates and the agonistic and antagonistic potencies of the peptides for in vitro steroidogenesis and inhibition of a synaptosomal protein kinase. A model for the cross-reactivity between ACTH and opioid peptides is discussed. 相似文献
987.
Epinephrine-promoted release of [3H]guanylylimidodiphosphate ([3H]Gpp(NH)p) from human platelet membranes has been used to probe the interactions between alpha2-adrenergic recpetors and Ni, the guanine nucleotide binding protein that couples those receptors to an inhibition of adenylate cyclase activity. We show here that ADP, which also acts through specific platelet receptors to inhibit adenylate cyclase activity, also promotes the release of [3H]Gpp(NH). The amount of [3H]Gpp(NH)-release elicited by epinephrine and by ADP together is equal to the sum of the amounts released by the two agents acting individually. Furthermore the maximal amounts of [3H]Gpp(NH)-release elicited by each of the two agents approximates the numbers of receptors for ADP and epinephrine present in the platelet membranes. These results suggest that the two receptor types interact with distinct portions of the pool of Ni molecules and that each receptor initiates guanine-nucleotide exchange on a single molecule of Ni. 相似文献
988.
Experimental observations reveal a number of characteristics of the redox-linked proton ejection from cytochrome c oxidase vesicles, which apparently cannot be explained by a proton pumping activity of the oxidase. These observations seem, on the other hand, to provide useful elements for alternative explanation(s) of the proton ejection. It is proposed here that the process is scalar and not vectorial and can derive from redox-linked rupture of protonated salt-bridges in the oxidase-lipid complex. 相似文献
989.
Induction of 2',5' oligo(A) synthetase in tumor-bearing mice with encephalomyocarditis (EMC) virus or poly(I)poly(C) 总被引:1,自引:0,他引:1
Infection of 13 month-old C3H mice with EMC virus or inoculation with the interferon inducer poly(I)poly(C) results in elevated levels of the enzyme 2',5' oligo(A) synthetase only in animals with spontaneous tumors (breast cancer or hepatomas). High enzymatic activities are detected in homogenates from liver, spleen, plasma and neoplastic cells of the animals with breast carcinomas and only in the neoplastic liver cells of the animals with hepatomas. 相似文献
990.
Dephosphorylation and reactivation of phosphorylated purified ox-kidney branched-chain dehydrogenase complex by co-purified phosphatase 总被引:7,自引:0,他引:7
The branched-chain 2 oxoacid dehydrogenase complex has been purified from well-washed ox-kidney mitochondria together with branched-chain dehydrogenase kinase. The complex was inactivated and phosphorylated by ATP in about 5 min at 30 degrees C. After hydrolysis of ATP by a contaminating ATPase (5-10 min) the complex was dephosphorylated and reactivated. Dephosphorylation and reactivation were linearly correlated. Reactivation was dependent upon Mg2+ (K0.5 greater than 1 mM) and inhibited completely by 50 mM fluoride. Reactivation and dephosphorylation are attributed to a mitochondrial branched-chain dehydrogenase phosphatase. 相似文献