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71.
L Rosa 《Biochemical and biophysical research communications》1979,88(1):154-162
Addition of ribose-5-phosphate to intact spinach chloroplasts in the absence of added Pi resulted in a conversion of part of the Benson-Calvin cycle into a linear sequence so that triose phosphate accumulated during CO2 fixation stoichiometrically with the O2 evolved (triose phosphate / O2 ratio was 2.0). The fortunate consequence of this effect is that the ratio may be calculated from the 3-phosphoglycerate and triose phosphate accumulated and the O2 evolved. In this way the ratio was shown to be 2.0, with cyclic or pseudocyclic phosphorylation contributing less than 9% to the total phosphorylation. 相似文献
72.
Photoinduced covalent cross-linking has been used to identify a common surface of four methionine-accepting tRNAs which interact specifically with the Escherichia coli methionine:tRNA ligase (EC 6.1.1.10). tRNA--ligase mixtures were irradiated, and the covalently linked complexes were isolated and digested with T1 RNase (Schimmel & Budzik, 1977). The fragments lost from the elution profile of the T1 RNase digest were considered to have been cross-linked to the protein and therefore in intimate contact with the enzyme. Only specific cognate tRNA--ligase pairs produce covalently linked complexes. The four substrate tRNAs used in this study have substantially different sequences, but all showed a common cross-linking pattern, supporting the view that the sites cross-linked to the enzyme reflect the functionally common contact surface rather than particularly photoreactivity regions of tRNA. The cross-linked contact surface is comprised of three regions: (1) the narrow groove of the anticodon stem and its extension into the anticodon loop; (2) the 3' terminal residues; and (3) the 3' side of the "T arm". Unlike previous studies with other tRNAs, the D arm is not involved and significant radiation damage is suffered by the tRNA which must be taken into account in the analysis. The results are consistent with and complement chemical modification studies [Schulman, L. H., & Pelka, H. (1977) Biochemistry 16, 4256]. 相似文献
73.
Protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) and cyclic adenosine 3',5'-monophosphate binding activities have been identified in zoospore extracts of the water mold Blastocladiella emersonii. More than 75% of these activities is found in the soluble fraction. Soluble protein kinase activity is resolved in three peaks(I, II and III) by DEAE-cellulose chromatography. Peak I is casein dependent and insensitive to cyclic AMP. Peak II is histone dependent and cyclic AMP independent; this enzyme is inhibited by the heat-stable inhibitor from bovine muscle. Peak III utilizes histone as substrate and is activated by cyclic AMP. 相似文献
74.
Adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) activity in Blastocladiella emersonii is associated with particulate subcellar fractions. Solubilization after treatment with detergent suggests its localization in a membrane fraction of the zoospore homogenate. The enzyme specifically requires Mn2+ for activity and is not stimulated by NaF. The kinetic characteristics of substrate utilization by B. emersonii adenylate cyclase were investigated with various concentrations of ATP and Mn2+, and in the presence of inhibitors. Plots of enzyme activity versus the actual concentration of the MnATP2- complex give sigmoid curves. An excess of Mn2+ activates the enzyme at low concentrations of substrate and leads to a modification of the enzyme kinetics. The nucleotides 5'-AMP and GTP were shown to be competitive inhibitors of the enzyme. In addition, kinetic data, obtained under conditions in which an inhibitor (ATP) is added in constant proportion to the variable substrate (MnATP2-) concentration, produced reciprocal plots that were linear and intersecting to the right of the ordinate, and secondary replots that were hyperbolic. These kinetic patterns support a model in which: MnATP2- is the substrate; free Mn2+ is an activator at low substrate concentrations, but an inhibitor at high substrate concentrations; and free ATP is not an efficient inhibiyor (Ki greater than 1.10(-4) M). 相似文献
75.
76.
Among 5 families with SBH of Neapolitan origin, herediatry glyco-lipidosis was accompanied in one by beta-thalassemia. All 10 members of this family, namely parents and 8 siblings, were investigated. The mother and two children were found to be carriers of both SBH and beta-thalassemia, while three other siblings were carriers of SBH alone. None of the six patients conformed the classic clinical picture often observed in genotypical SBH. The present state of genotypic transmission of the stigma is discussed on the basis of the author's experience as well as the data in the literature. As for the combination SBH-thalassemia in the same individual it may be concluded that the two genes are most likely independent and certainly not linked. 相似文献
77.
M Goossens M C Garel J Auvinet O Basset P Ferreira Gomes J Rosa N Arous 《FEBS letters》1975,58(1):149-154
78.
79.
Marina Rovani Drummond Luciene Silva dos Santos Renata Soalheiro Fvaro Raquel Silveira Bello Stucchi Ilka de Ftima Santana Ferreira Boin Paulo Eduardo Neves Ferreira Velho 《PLoS neglected tropical diseases》2022,16(7)
BackgroundThis study aimed to assess the prevalence of Bartonella sp.-DNA detection in blood and skin samples from patients with non-viral end-stage liver disease awaiting liver transplantation.Methodology/Principal findingsBlood samples and healthy skin fragments from 50 patients were tested using microbiological and molecular methods. Fifteen patients had cryptogenic hepatitis (CH) and 35 had alcoholic, drug-induced or autoimmune liver disease. DNA was extracted from whole blood and liquid culture samples, isolates, and skin fragments. Thirteen of the 50 patients (26%) had Bartonella henselae DNA detection in their blood (9/50) and/or skin (5/50) samples. Colonies were isolated in 3/50 (6%) and infection was detected in 7/50 (14%) of the 50 patients. B. henselae-DNA detection was more prevalent in patients with CH than in other patients (p = 0.040). Of 39 patients followed-up for at least two years, a higher mortality rate was observed among patients with CH infected with B. henselae (p = 0.039).Conclusions/SignificanceFurther studies assessing the role of B. henselae infection in the pathogenesis of hepatitis patients must be urgently conducted. 相似文献
80.
Paula Martínez Raúl Snchez-Vzquez Iole Ferrara-Romeo Rosa Serrano Juana M. Flores Maria A. Blasco 《PLoS genetics》2022,18(6)
The shelterin protein POT1 has been found mutated in many different familial and sporadic cancers, however, no mouse models to understand the pathobiology of these mutations have been developed so far. To address the molecular mechanisms underlying the tumorigenic effects of POT1 mutant proteins in humans, we have generated a mouse model for the human POT1R117C mutation found in Li-Fraumeni-Like families with cases of cardiac angiosarcoma by introducing this mutation in the Pot1a endogenous locus, knock-in for Pot1aR117C. We find here that both mouse embryonic fibroblasts (MEFs) and tissues from Pot1a+/ki mice show longer telomeres than wild-type controls. Longer telomeres in Pot1a+/ki MEFs are dependent on telomerase activity as they are not found in double mutant Pot1a+/ki Tert-/- telomerase-deficient MEFs. By using complementation assays we further show that POT1a pR117C exerts dominant-negative effects at telomeres. As in human Li-Fraumeni patients, heterozygous Pot1a+/ki mice spontaneously develop a high incidence of angiosarcomas, including cardiac angiosarcomas, and this is associated to the presence of abnormally long telomeres in endothelial cells as well as in the tumors. The Pot1a+/R117C mouse model constitutes a useful tool to understand human cancers initiated by POT1 mutations. 相似文献