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991.
Inhibition of ADP-ribosylation of histone by diadenosine 5', 5"' -p (1), p(4)-tetraphosphate 总被引:3,自引:0,他引:3
Y Tanaka N Matsunami K Yoshihara 《Biochemical and biophysical research communications》1981,99(3):837-843
Diadenosine 5′, 5?-p1, p4-tetraphosphate (Ap4A) strongly inhibited ADP-ribosylation reaction of histone by purified bovine thymus poly(ADP-ribose) polymerase. This compound showed a relatively weak inhibitory effect on Mg2+-dependent, enzyme-bound poly(ADP-ribose) synthesis. Among various adenine nucleotides tested, including several diadenosine nucleotides with varying phosphate chain length, Ap4A was the most effective inhibitor of the histone-modification reaction. Ap5A and Ap6A showed slightly lower inhibitory effect than Ap4A. Kinetic analysis of the inhibitor (Ap4A) with varying concentration of substrate (NAD+) revealed that this compound is a “mixed type inhibitor”, with a Ki value of 5.1 μM. 相似文献
992.
The amino reagent 2,4,6-trinitrobenzenesulfonate (TNBS) was found to inactivate mitochondrial F1-ATPase through covalent labeling, which was not reversed by dithiothreitol. The observed rate of inactivation was retarded by inorganic phosphate, but enhanced by prior labeling of F1 with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-C1). These observations are consistent with the presence of an essential amino group near the bound inorganic phosphate at the catalytic site of F1. A comparison of the observed protection of F1 from NBD-C1 and 5′-p-fluorosulfonyl-benzoyladenosine (FSBA) respectively by inorganic phosphate and by 2′,3′-O-(2,4,6-trinitrophenyl)adenosine 5′-monophosphate (TNP-AMP) suggests that NBD-C1 labels an essential Tyr residue in the positively charged locus for binding the polyphosphate end of ATP, and that FSBA labels an essential Tyr residue in the more hydrophobic locus for binding the adenosine moiety of ATP at the catalytic site of F1. 相似文献
993.
Spondyloepiphyseal dysplasia, chondroitin sulfate type: a possible defect of PAPS--chondroitin sulfate sulfotransferase in humans 总被引:4,自引:0,他引:4
Paulo A.S. Mourão Setuko Kato Patricia V. Donnelly 《Biochemical and biophysical research communications》1981,98(2):388-396
Four patients with an unusual form of spondyloepiphyseal dysplasia excreted in the urine undersulfated chondroitin 6-sulfate (Biochem. Med. , 415–423, 1973). The sera of these patients show a low activity of PAPS — chondroitin sulfate sulfotransferase, while the undersulfated chondroitin sulfate present in their urine is a much better acceptor of than standard chondroitin sulfate when they are incubated with []PAPS and normal sulfotransferases. These results suggest that in these patients the skeletal lesions are secondary to a defect in the synthesis of chondroitin sulfate involving specifically the sulfotransferase activity. 相似文献
994.
Immunological properties of ligandin(Lig) and glutathione S-transferase(GST)-A, -AA and -B were investigated for elucidating their subunit relationships. By using either anti-Lig or -AA antibody, GST-B made a clear common precipitin line with Lig or AA in double immunodiffusion and the activity was inhibited intermediately between Lig and AA, whereas Lig and AA reacted very weakly with antibodies to each other. A hybrid between Lig and AA formed by guanidine hydrochloride treatment was identified immunochemically to be GST-B. GST-A had no immunological relationship with any of other three forms. 相似文献
995.
Hans-Dietrich Heilmann Maria Holzner 《Biochemical and biophysical research communications》1981,99(4):1146-1152
To achieve specific cross-linking between the active sites of the non-identical subunits tryptophan synthase from E. coli was modified by a novel method. After reaction with bifunctional reagents of the isolated subunits at their active sites, the tetrameric complex was formed and the free ends of the reagent molecules reacted with each other forming a covalent bridge between the subunits. The distance between the amino acid side chains involved in the cross-linking should not exceed approx. 1.8 nm. A distance much shorter than that is unlikely since all attempts to cross-link the active sites with different shorter bifunctional reagents failed. The implications of these results in the mechanism of action of the enzyme are discussed. 相似文献
996.
Douglas L. Currell Bernice Law Michael Stevens Paul Murata Carmela Ioppolo Filippo Martini 《Biochemical and biophysical research communications》1981,102(1):348-354
Human hemoglobin reacts with 4-Isothiocyanatobenzene sulfonic acid at the four amino groups of the N-terminal valines. The modified protein shows a decreased oxygen affinity over a wide pH range, a reduced alkaline Bohr effect, decreased co-operativity, and a reduced effect of inositol hexasulfate on the oxygen affinity. 相似文献
997.
Hajime Tokuda Tsutomu Unemoto 《Biochemical and biophysical research communications》1981,102(1):265-271
The membrane potential generated at pH 8.5 by K+-depleted and Na+-loaded is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na+-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na+ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na+-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na+ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na+ chemical gradient. 相似文献
998.
In the liver of rats fed the azocarcinogen 3'-methyl-4-dimethylaminoazobenzene (3'MeDAB) reiterated RNA sequence transcribed from middle repetitive DNA are released into the cytoplasm. The same repetitive nucleotide sequences can be isolated from the chromatin of the liver of control animals in the form of metabolically highly active, 13 000 daltons RNA. This small, chromatin-associated RNA originates from nuclear RNA larger than 10 S. The discontinuation of the feeding of the azocarcinogen will not stop the release of the nuclear reiterated RNA sequences into the cytoplasm. The repetitive sequences of nuclear RNA which are released into the cytoplasm in animals fed the azocarcinogen can no longer be found in the chromatin in the form of small RNA molecules. The results can be explained by the assumption that the reiterated RNA sequences are involved in the upholding of RNA processing. A cell-specific processing of RNA will be maintained by the interaction of reiterated RNA fragments from already processed RNA with the reiterated complementary sequences on RNA yet to be processed. Existence of such a feed-back circuit would make it possible to explain how a temporary interference of the azocarcinogen with RNA processing will result in the disappearance of specific reiterated RNA sequences from the chromatin. It could also explain the continuation of the release of the same repeated RNA sequences into the cytoplasm as part of larger RNA molecules even after the removal of the carcinogen. 相似文献
999.
1000.
Patrick De Wever 《Geobios》1981,14(1):5-15
Studies of skeleton elements of several jurassic species of Saitoum allow to compare them with Poulpus from Trias. The sub-family Poulpinae is introduced, caracterised by three cephalic arcs and the collar position of the cephalic structure. Among the jurassic forms, 4 species are newly described: S. corniculum, S. elegans, S. levium and S. trichylum. 相似文献