共查询到20条相似文献,搜索用时 15 毫秒
1.
, the initial membrane enzyme in the biosynthesis of peptidoglycan, requires a lipid microenvironment for function. was reversibly intercalated into membranes to perturb the hydrophobic interactions in this microenvironment in order to define further the role of lipid. In the concentration range for maximal stimulation of enzymic activity (0.12–0.18 M), causes a 40% decrease in the fluorescence emission of the dansylated product, undecaprenyl . Since no change in emission maximum occurs below 22°C in the presence of 0.12 M , it is concluded that intercalation of this alkanol causes an increase in fluidity. Above 22°C this concentration of causes both a decrease in the fluorescence emission and a red shift in the emission maximum. It is concluded that a polarity change as well as fluidity change occurs above 22°C. also causes a significant change in the phase transition experienced by the dansylated lipid product. Thus, it is possible with , e.g. , to perturb lipid-translocase interactions resulting in an increase in fluidity in the microenvironment of the enzyme. This change in fluidity correlates with a stimulation of enzymic activity. 相似文献
2.
Claudia Moore Merle L. Blank Ten-Ching Lee B. Benjamin Claude Piantadosi Fred Snyder 《Chemistry and physics of lipids》1978,21(3):175-178
In previous studies on the modification of polar head groups of membrane phospholipids with the unnatural base analog, , we reported an unidentified phospholipid in addition to in the various membrane fractions of rat liver. The structure of this phospholipid has now been identified as by nuclear magnetic resonance spectroscopy, and by chromatographic and enzymic analysis. In addition, we found that when rats were injected intraperitoneally with the , 19% of teh liver microsomal phospholipid was . 相似文献
3.
Sylvette Bas Elisabeth Imesch Daniel Ricquier Françoise Assimacopoulos-Jeannet Josiane Seydoux Jean-Paul Giacobino 《Life sciences》1983,32(18):2123-2130
The activities of the main enzymes involved in fatty acid utilization i.e. palmitoyl CoA synthetase as well as peroxisomal and mitochondrial β-oxidation were measured in brown adipose tissue homogenates of lean and / mice kept at 23°C or acclimated at 4°C. The proton conductance pathway, i.e. the number of purine nucleotide (GDP) binding sites and the percentage of 32,000 polypeptide in brown adipose tissue mitochondria were also measured. In the if/ mice at 23° C, the specific activities of the palmitoyl CoA synthetase and of the β-oxidation as well as the number of GDB binding sites were lower than in the lean mice by 26%, 43% and 37%, respectively. The percentage of 32, 000 polypeptide, however, was the same in both groups. In the / mice at 23° C, the lower homogenate β-oxidation specific activity was due to the fact that the peroxisomal and mitochondrial specific activities were 44% and 37% lower, respectively. Cold acclimation at 4° C was found to cause an increase of the palmitoyl CoA synthetase specific activity, of the palmitoyl CoA synthetase and peroxisomal β-oxidation total activities and of the number of GDP binding sites, in both lean and / mice. Cold acclimation increased the percentage of 32,000 polypeptide in the / mice only. 相似文献
4.
Short, mild treatments of sarcoplasmic reticulum vesicles with aqueous from methanol to caused an inhibition of calcium uptake and an enhancement of ATPase activity. The treatments increased both calcium-dependent (extra) ATPase activity and calcium-independent (basic) ATPase activity of vesicles. The apparent initial reaction rate of ATPase of vesicles was about twice that of control vesicles. With increasing number () of carbon atoms of the , the maximum increment of ATPase activity increased, and both the alcohol concentration () required to inhibit calcium uptake by 50% and the alcohol concentration () required to enhance ATPase activity by 50% of the maximum increment of ATPase activity decreased as follows. The ratio, to , was constant for all values. The apparent free energy of binding of the methylene groups of to sarcoplasmic reticulum vesicles was evaluated (?796 cal/mole) and compared with data from the partition of in octanol and water (?670 cal/mole). The effects of on membrane vesicles are discussed on the basis of these data. 相似文献
5.
J.J. Schrijen A. Omachi W.A.H.M. Van Groningen-Luyben J.J.H.H.M. De Pont S.L. Bonting 《生物化学与生物物理学报:生物膜》1981,649(1):1-12
(1) The total phospholipid content of a gradient purified ()-ATPase preparation from pig gastric mucosa is 105 μmol per 100 mg protein, and consists of 29% sphingomyelin, 29% phosphatidylcholine, 28% phosphatidylethanolamine, 10% phosphatidylserine and 4% phosphatidylinositol. The cholesterol content corresponds to 50 μmol per 100 mg protein. (2) Treatment with phospholipase C (from Clostridium welchii and Bacillus cereus) results in an immediate decrease of the phosphate content. Up to 50% of the phospholipids are hydrolyzed by each phospholipase C preparation alone, without further hydrolysis by increased phospholipase concentration or prolonged incubation time. Combined treatment with the two phospholipase C preparations, sequentially or simultaneously, hydrolyzes up to 65% of the phospholipids. (3) The ()-ATPase and K+ stimulated activities are decreased proportionally with the total phospholipid content, indicating that these enzyme activities are dependent on phospholipids. (4) Phospholipase C treatment does not change optimal pH, value for ATP and temperature dependence of the gastric ()-ATPase, but slightly decreases the value for K+. (5) Phospholipase C treatment lowers the binding and phosphorylation capacities, suggesting that inactivation occurs primarily on the substrate binding level. (6) Most of the results can be understood by assuming that hydrolysis of the phospholipids by phospholipase C leads to aggregation of the membrane protein molecules and complete inactivation of the aggregated ATPase molecules. 相似文献
6.
The specific synthesis of F mRNA directed by the F gene carried on the specialized transducing bacteriophage F, performed , is described with the use of an S180 extract from a strain carrying R?. Synthesis of F mRNA is biphasic at approximately 7 minutes. The regulation of F mRNA synthesis by the specific arginine holorepressor present in an S180 extract prepared from a strain carrying the R+ allele is described. 相似文献
7.
OKY-1581 is an effective inhibitor of thromboxane synthesis and . The generation of thromboxane B2 (TxB2), prostaglandin E (PGE) and prostaglandin F (PGF) was measured following clotting and during platelet aggregation induced by collagen. The presence of OKY 1581 either or caused a reduction in TxB2 generation during clotting and platelet aggregation with a concomitant increase in PGE and PGF. The effect could be observed two hours after oral or subcutaneous administration of 5 to 100 mg per rabbit and lasted for 24 to 48 hours. The reduction in TxB2 was not accompanied by an inhibition of clotting or platelet aggregation. OKY-1581 appears to be a suitable agent for studying the role of TxB2 in atherosclerosis. 相似文献
8.
George M. Stancel Judy S. Ireland Venkat R. Mukku Alice K. Robison 《Life sciences》1980,27(12):1111-1117
The pesticide o,p'-DDT stimulates the production of a specific uterine protein, the so-called induced protein or IP, normally associated with an estrogenic response of the uterus. stimulation of IP production is observed 1 hour after the administration of 250 mg/kg of o,p'-DDT to immature rats. stimulation of IP production is observed after a 1 hour incubation of uteri with 100 μM o,p'-DDT. This response is blocked by Actinomycin D. In contrast to o,p'-DDT, which binds to the cytoplasmic estrogen receptor and stimulates IP production, p,p'-DDT which does not bind well to the estrogen receptor does not stimulate IP production . These findings represent the first report of an estrogenic effect of o,p'-DDT in a completely system. 相似文献
9.
Ronald M. Hamelik Mead M. McCabe 《Biochemical and biophysical research communications》1982,106(3):875-880
An inhibitor of , endodextranase was detected in proteins prepared from batch cultures of , strains representing serotypes through . Affinity chromatography of strain 6715-49 proteins, which apparently were free of endodextranase activity, yielded an active endodextranase and, in a separate peak, the endodextranase inhibitor. The presence of the inhibitor in culture fluids accounts for the absence of endodextranase activity in batch-grown cultures of , known to produce this enzyme. 相似文献
10.
Purified cytochrome from bovine adrenocortical mitochondria was incorporated into liposomes by the cholate-dilution method utilizing either dialysis or Sephadex gel filtration. Among synthetic phospholipids tested, dioleoylglycerophosphocholine showed the best stability during the incorporation of into liposomes. A maximum amount of heme was incorporated into liposomes at a molar ratio of phospholipid to the cytochrome of approx. 200. When was incorporated into the dioleoylglycerophosphocholine liposomes by the cholate-filtration method, the showed two major populations on the elution pattern of the Sepharose 4B gel filtration, and were seen at a diameter of 200–600 Å and its aggregated forms. When the cytochrome was incorporated into dioleoylglycerophosphocholine liposomes or cholesterol-free adrenocortical mitochondrial liposomes, was less stable than in aqueous solution. Cholesterol or adrenodoxin markedly stabilized the liposomal . Liposomal required cholesterol for its optimum reduction with adrenodoxin, adrenodoxin reductase, and NADPH in the presence of CO. About 70% of the total heme in the dioleoylglycerophosphocholine liposomes was reduced by the enzymatic reduction in the presence of cholesterol, indicating that 70% of the total molecules are exposed to the surface of the outer monolayer. In order to see the location of the heme in membrane, the dioleoylglycerophosphocholine-liposomal was subjected to treatment. This reagent destroyed the liposomal . These results suggest that the heme is located in the proximity of the reacting sites which are exposed to the surface, or located on the vincinity of polar heads of the membrane. 相似文献
11.
Joseph J. Defrank Douglas W. Ribbons 《Biochemical and biophysical research communications》1976,70(4):1129-1135
A mutant strain (PL pT ) of PL, has been isolated for its inability to growth with -cymene as carbon source. The mutant oxidizes (and -cumate) to a compound (λmax 293 nm) which is readily converted to 3-hydroxy--cumate by acid. 4-Trifluoromethylbenzoate is oxidized by the mutant to an acid-stable intermediate (λmax 277nm) that has been crystallized. The spectral properties (u.v., i.r., NMR and mass) of this metabolite are consistent with those expected for a 2,3-dihydro-2,3-dihydroxy derivative of 4-trifluoromethylbenzoate. Further support of this structure was provided by elemental analysis and the properties of two derivatives of the metabolite, 4-trifluoromethyl-3-hydroxybenzoate and an acetonide formed with 2,2-dimethoxypropane. The stability of a product obtained by treatment of the dihydrodiol metabolite with triacetylosmate indicates that it is the . 相似文献
12.
Ken F. Jarrell Andrew M. Kropinski 《Biochemical and biophysical research communications》1981,99(4):1185-1190
Lipopolysaccharides (LPS) isolated from various rough derivatives of strains were found to neutralize coliphage T7. Concentrations of 0.4 – 17 μg LPS/ml were sufficient for 50% inactivation of T7 within 1 hour. From the LPS analyses of the mutants, it is believed that T7 may be binding to the heptose region of LPS, suggesting a similarity in structure between the heptose regions of and LPS. 相似文献
13.
Both pairs of -ll-desoxy- and -13---15, 16-dihydroxyprostaglandins have been synthesized via 1,4-conjugate additions of an appropriately functionalized -vinyl cuprate to the requisite cyclopentenone. These prostaglandin analogs are considerably less potent than PGE2 as gastric secretion inhibitors or as bronchodilators. 相似文献
14.
Anthony E. Pegg 《Biochemical and biophysical research communications》1978,84(1):166-173
Extracts from various rat tissues were incubated with [3H]methylated DNA or chromatin in order to compare their abilities to catalyze the removal of labeled -methylguanine from acid precipitable DNA. Liver extracts had the greatest activity. Kidney extracts had about 35% of the activity in liver and extracts from lung, colon, small intestine and brain were much less active. The enzyme responsible for this reaction does not appear to be an -glycosidase because no labeled -methylguanine could be detected in the supernatant fraction even though more than 50% of this base was lost from the DNA. The released radioactivity was present as methanol which is consistent with the possibility that the reaction may involve a demethylase action on either the DNA substrate or an oligonucleotide derived from it. 相似文献
15.
A family of plasmid cloning vectors has been constructed that make use of the leftward promoter () of phage λ to provide for efficient expression of cloned genes in Escherichia coli. The promoter activity of is fully repressed at low temperature by a thermolabile repressor product of the gene, and can be activated by heat induction. Examples are given (β-lactamse, tryptophan synthetase A) where, under optimal conditions, between 30 and 40% of the total protein synthesis is directed by the cloned gene under control. 相似文献
16.
Robert P. Hanzlik Steven Heideman Debbie Smith 《Biochemical and biophysical research communications》1978,82(1):310-315
The hydration of -β-methylstyrene oxide, -2,3-octene oxide, and their 18O-enriched forms by epoxide hydrase of rat liver microsomes has been investigated. Both epoxides underwent quantitative enzymatic hydration yielding exclusively the corresponding diols, indicating that complete stereochemical inversion at a single oxirane carbon had occurred. Mass spectral analysis of diols formed enzymatically from the 18O enriched epoxides indicated they were formed with great regioselectivity, 89% and 85% of the 18O being located at the benzylic carbon of the styrene diol and at C-3 of the octane diol, respectively. 相似文献
17.
Dorothy A. Schafer Donald E. Hultquist 《Biochemical and biophysical research communications》1980,95(1):381-387
Microsomal NADH-cytochrome reductase has been purified from bovine liver by an improved procedure which employs affinity chromatography on ADP-agarose in combination with anion exchange chromatography. The reductase was extracted from a 105,000 × microsomal pellet with Triton X-100. The overall purification from isolated microsomes was 98-fold and the yield was 10%. The preparation was nearly homogeneous on SDS-PAGE. This procedure requires less time and effort than previously described procedures. Partially purified cytochrome is also obtained. 相似文献
18.
P.N. Bandyopadhyay Maharani Chakravorty 《Biochemical and biophysical research communications》1976,71(2):644-650
Infection of with the mutant of bacteriophage P22 leads to a rapid and severe efflux of intracellular leucine. The superinfection exclusion () genes of P22 interfere with the function of gene, the product(s) of which is speculated to be an internal protein of phage P22. 相似文献
19.
Jerry M. Buysse Sunil Palchaudhuri 《Biochemical and biophysical research communications》1982,106(3):748-755
The minichromosome pWS6 was unstable in , K-12 but became stable upon transfer to ,. The instability of pWS6 was restored when pWS6 was brought back to ,, an observation consistent with the proposed phenomena of chromosomal incompatibility. 相似文献
20.
We have measured the fluorescence decay of using the phase-modulation method, in several solvent systems and egg phosphatidylcholine vesicles. The decay is monoexponential in pure solvents (both polar and non-polar) of low viscosity. In polar viscous solvents or in non-polar solvents containing an added polar solute, the decay is heterogeneous and emission wavelength dependent. In such cases, dielectric relaxation and/or excited-state complexing give rise to a shift of the emission spectrum on the nanosecond time scale. Emission-wavelength-dependent decay was also observed when was bound to egg phosphatidylcholine vesicles. From these results as well as the position of the emission spectral maximum, we conclude that probes the ester-carbonyl region of the phospholipid acyl chains, where it undergoes an excited-state reaction. This result contradicts the often made assumption that probes the deeper hydrocarbon region of the bilayer. 相似文献