共查询到20条相似文献,搜索用时 31 毫秒
1.
J G Surak 《Life sciences》1977,20(10):1735-1740
The molecular toxicity of monotertiarybutylhydroquionone (TBHQ) was studied using as a model cell system. TBHQ at 26 ppm in the media inhibited cell growth by 50%. TBHQ inhibited the oxidation of 14C-acetate to 14CO2. In addition, increasing concentrations of TBHQ decreased the incorporation of 14C-acetate into lipids and protein, 14C-amino acids into protein, 3H-uridine into RNA and 3H-thymidine into DNA. The incorporation of 14C-acetate into glycogen increased with concentrations up to 20 ppm TBHQ in the media while glycogen synthesis decreased with 40 ppm TBHQ. 相似文献
2.
G P van Heusden H van den Bosch 《Biochemical and biophysical research communications》1979,90(3):1000-1006
Lysophospholipase-transacylase from rat lung catalyzes the transfer of palmitate from 1-palmitoyl--glycero-3-phosphocholine to water and to another molecule of 1-palmitoyl--glycero-3-phosphocholine. Incorporation of palmitate into phosphatidylcholine is restricted to palmitate donated by lysophosphatidylcholine, free palmitate cannot be esterified to lysophosphatidylcholine by the enzyme. Experiments in the presence of H218O and mass spectrometric analysis of the reaction products show that 18O is incorporated into the released palmitate but not into the transesterification product phosphatidylcholine. This proofs that the hydrolytic reaction proceeds by O-acyl cleavage. Furthermore, the results strongly suggest that transfer of palmitate to lysophosphatidylcholine occurs through an intermediary covalent acyl-enzyme complex. 相似文献
3.
A Araya M Krauskopf M A Siddiqui 《Biochemical and biophysical research communications》1975,67(3):924-934
Transfer RNA with methionine acceptor activity isolated from two distinct physiological stages of the developing posterior silkgland of the silkworm, , was examined. The tRNA from both stages could be fractionated on benzoylated DEAE-cellulose colum into two iso-accepting species, tRNA1Met and tRNA2Met. The molar quantity per gland of tRNA1Met species, which was also formylatable with the enzymes, increased twelve-fold as the gland differentiates to produce a large amount of a single protein, silk-fibroin. Since methionine is not a part of silk-fibroin, the preferential increase in tRNA1Met content would reflect the increased biological activity and the rapid rate of protein synthesis during the terminal differentiation of posterior silkgland. 相似文献
4.
A Rosner K M Jakob J Gressel D Sagher 《Biochemical and biophysical research communications》1975,67(1):383-391
A 0.5 × 106r RNA found in plastids of the aquatic angiosperm , is synthesized at a much higher rate than any other rapidly labeling RNA species about h after dark-grown plants are transferred to light. The pulse labeling kinetics of the 0.5 × 106r RNA after transfer to light, argue against its involvement in the biogenesis of plant rRNAs. Although poly(A) RNA is found in , poly(A) sequences are not detected in the 0.5 × 106r RNA; yet a sucrose gradient fraction which includes RNA of this r stimulates amino acid incorporation by an cell free extract more than other RNA fractions. The possible involvement of the 0.5 × 106r RNA as a chloroplast messenger is discussed. 相似文献
5.
Olga Genbačev Marija Ratković Miodrag Krainčanić Vojin Šulović 《Prostaglandins & other lipid mediators》1977,13(4):723-733
The biosynthesis of placental proteins and placental lactogen (HPL) was studied in 10–12 week, 16–18 week and term human placenta in the presence and absence of PGE2α. The highest 14C-leucine incorporation was detected in 10 to 12 weeks old placentas. Addition of PGE2α to the induction medium depressed the rate of incorporation of 14C-leucine into placental proteins on a dose dependent manner. Placentas most sensitive to this action of PGE2α were those obtained at 18 weeks gestation followed by placentas at term. application of PGE2α for tharapeutic induction of abortions resulted in the marked inhibition of placental protein synthesis . 相似文献
6.
S.B. Hladky 《生物化学与生物物理学报:生物膜》1974,352(1):71-85
The experimental steady-state current-voltage relations for low concentrations of a neutral carrier and an ion may be fitted theoretically either by assuming a form for the potential dependence of the rate of transfer of complex across the membrane and adjusting the proposed nature of the association-dissociation reactions or by assuming equilibrium for the association and adjusting the potential dependence of the transfer process. Different dependences for the rate of transfer correspond, at least formally, to different shapes for the potential energy barrier which the complex must cross. By comparing measurements of the current-voltage relations for non-actin with Na+, K+, and NH4+, it is possible to distinguish between the effeects of the various rates. For black lipid membranes made from glycerolmonooleate+, the potential energy barrier is high with a narrow top, but the rate of association still becomes increasingly limiting for Na+, K+ and NH4+, in the order given. For bacterial phosphatidylethanolamine, with the barrier is much wider and no effect of the rate of association can be detected. 相似文献
7.
Synthesis of diphtheria toxin in E. coli cell-free lysate 总被引:7,自引:0,他引:7
An cell-free lysate was used to translate RNA from nontoxinogenic C7(?), C7 infected with β tox+ corynebacteriophage, and strain PW8. De novo synthesis of toxin was detected by immune precipitation with antitoxin, ADP-ribosylation of mammalian elongation factor 2 and rabbit skin test. The results indicated that toxin is produced in the protein synthesizing system primed with RNA from cells infected with tox+ bacteriophage and is absent in systems primed with RNA from C7(?) cells. 相似文献
8.
Tetsuo Sawai Laura J. Crane J.O. Lampen 《Biochemical and biophysical research communications》1973,53(2):523-530
The plasma membrane-bound penicillinase of has been purified. Amino acid analysis showed no significant differences in composition between the enzyme and exopenicillinase. Enzyme purified from cultures containing H333PO4 or [3H]-glycerol contained 33P or [3H]-glycerol activity and treatment with 8 M urea, 0.2% sodium dodecyl sulfate at 80° C did not remove the 3H-activity from the enzyme protein. Trypsin readily cleaved the glycerol-containing moiety from the enzyme protein, forming enzyme with molecular weight and heat stability like that of the exoenzyme. Phospholipase D and C also produced enzyme resembling the exo-form. 相似文献
9.
The 0.5M KCl wash of rabbit reticulocyte ribosomes (I fraction) catalyzes the deacylation of Met-tRNAfMet. Upon DEAE-cellulose column chromatography, the deacylase activity elutes with the 0.1M KCl wash of the column (f1) and is well-resolved from the peptide chain initiation factors (1–3). The deacylase activity is specific for Met-tRNAfMet (retic., ). Other aminoacyl tRNAs tested including fMet-tRNAfMet (retic., ), Phe-tRNA (), Val-tRNA (retic.), and Arg-tRNA (retic.) are completely resistant to the action of the deacylase. In the presence of the peptide chain initiation factor (IF1) and GTP, retic. Met-tRNAfMet forms the initiation complex Met-tRNAfMet:IF1:GTP (2), and in this ternary complex Met-tRNAfMet is not degraded by the deacylase. Met-tRNAfMet binds to IF1 independent of GTP, and in this complex, this Met-tRNAfMet is degraded by the deacylase.Prior incubation of f1 with Met-tRNAfMet (retic.) strongly inhibited protein synthesis initiation, presumably due to deacylation of the initiator tRNA. This inhibition by f1 was completely prevented when Met-tRNAfMet (retic.) was pre-incubated with peptide chain initiation factors. 相似文献
10.
R.C. Scarpulla C.E. Deutch R.L. Soffer 《Biochemical and biophysical research communications》1976,71(2):584-589
Leucyl, phenylalanyl-tRNA-protein transferase also catalyzes transfer of methionyl residues as indicated by (i) copurification over a 1000-fold range of transfer activities for all three amino acids and (ii) loss of methionyl transfer activity in a mutant of lacking the transferase and reappearance of this activity in a transferase revertant. The purified enzyme was found to use Met-tRNAmMet in preference to Met-tRNAfMet as donor substrate. Peptides containing a basic amino acid at the NH2-terminus functioned as acceptors for the transfer of methionyl residues. 相似文献
11.
Heterogeneous electron transfer rate constants were determined as a function of electrode potential for one-electron oxidation in acetonitrile (AN) at O °C of a series of organocobaloximes [R-Co(DH)2L] bearing widely different organic groups. Reaction entropies were determined by voltammetric half-wave potential (Er) measurements in a non-isothermal cell. The electron transfer coefficients and reorganization parameters were calculated following the Marcus theory. The reaction free energies relative to a reference couple ΔG° are linearly correlated with the polar Taft constant of the organic substituent R.The steric effects on ΔG° are shown by the correlation of Er with the CoC bond distance.Assuming constancy of double layer effects along the series in the given solution composition, the trends of the apparent rate constants kapp were considered in order to evaluate the effects of the nature of the organic ligand on the activation energy ΔG3 of the electron transfer. The steric effects on ΔG3 are pointed out i.a. by consideration of the relationship between ΔG3 and ΔG°. 相似文献
12.
Aflatoxin B1-2,3-oxide: evidence for its formation in rat liver in vivo and by human liver microsomes in vitro 总被引:12,自引:0,他引:12
D H Swenson E C Miller J A Miller 《Biochemical and biophysical research communications》1974,60(3):1036-1043
Injection of [3H]aflatoxin B1 into rats yielded covalently bound derivatives in hepatic DNA, rRNA, and protein. Mild acid hydrolysis of the DNA and rRNA adducts formed a derivative indistinguishable from 2,3-dihydro-2,3-dihydroxy-aflatoxin B1. The data indicate that approximately 60% of the nucleic acid adducts were derived from reactions with aflatoxin B1-2,3-oxide. Acid hydrolysis of rRNA-[3Haflatoxin B1 adduct formed by human liver microsomes also liberated the dihydrodiol in significant amount. The 2,3-oxide of aflatoxin B1 is a probable ultimate carcinogenic metabolite. 相似文献
13.
J Germershausen D Goodman E W Somberg 《Biochemical and biophysical research communications》1978,82(3):871-878
RNA (guanine-7) methyltransferase, partially purified from mycelia, catalyzed the transfer of the methyl group from S-adenosylmethionine to the 5′ terminus of both poly A(+) RNA and reovirus unmethylated mRNA. RNase T2 digestion of the methylated poly A(+) RNA from yielded the “cap” structures m 7G(5′)pppAp and m 7G(5′)pppGp in a ratio of 2:1 respectively. RNase T2 digestion of the methylated reovirus mRNA yielded m 7G(5′)pppGp exclusively. The absence of mRNA 2′-0-methyltransferase activity in the enzyme preparation is consistent with the absence of 2′-0-methylation in mRNA [Seidel, B. L. and Somberg, E. W. (1978) Arch. Biochem. Biophys. , 108–112]. This is the first isolation of an eucaryotic, cellular RNA (guanine-7) methyltransferase that has been shown to methylate homologous substrate. 相似文献
14.
Phosphorylation of high mobility group proteins 14 and 17 by nuclear protein kinase NII in rat O6 glioma cells 总被引:1,自引:0,他引:1
J J Harrison R A Jungmann 《Biochemical and biophysical research communications》1982,108(3):1204-1209
High mobility group (HMG) proteins 14 and 17 of rat C6 glioma cells are phosphorylated on both serine and threonine. In HMG 14 about 60% of the total [32P]phosphate was identified as phosphoserine and 40% as phosphothreonine. In HMG 17, there was 88% phosphoserine and 12% phosphothreonine. Glioma cell nuclear protein kinase NII phosphorylates HMG 14 and 17 on serine as well as threonine and the relative percentages of [32P]phosphoamino acid are similar to those seen . Nuclear protein kinase NI and the type I and II cAMP-dependent protein kinases exhibit only minor phosphorylating activity towards HMG 14 and 17. We conclude that nuclear protein kinase NII is responsible for the phosphorylation of HMG 14 and 17 . 相似文献
15.
Clinton O. Chichester George C. Fuller 《Biochimica et Biophysica Acta (BBA)/General Subjects》1979,586(2):341-356
The turnover rates of prolyl hydroxylase and immunologically related (cross reacting) protein were examined using labeled leucine as precursor or by measuring the decay of elevated prolyl hydroxylase and immunologically cross-reacting protein back to basal levels. Prolyl hydroxylase and immunologically cross-reacting protein were purified from neonatal rabbit skin at various times following the administration of [3H]leucine. Prolyl hydroxylase was purified by affinity chromatography. Immunologically cross-reacting protein was purified by antibody precipitation from the dialyzed 70% (NH4)SO4 supernatants and subsequent electrophoresis on 10% sodium dodecyl sulfate-polyacrylamide slab gels. The radioactivity of the species isolated, which corresponded to the two major subunits of prolyl hydroxylase, was used in the turnover studies of immunologically cross-reacting protein. The peak incorporation of label into prolyl hydroxylase was found to be 12 h while for immunologically cross-reacting protein this occured within 2 h. The loss of radioactivity from these protein pools denotes an apparent for prolyl hydroxylase of 73 h and a for immunologically cross-reacting protein of 53 h. From the specific activity of free skin leucine pools, the effect of reutilization could be corrected and a true for prolyl hydroxylase of 45 h was determined. The values of these proteins were determined by a second method in which prolyl hydroxylase and immunologically cross-reacting protein in the aorta and liver of adult male rabbits were elevated by daily epinephrine-thyroxine treatment for 12 days. The decline of prolyl hydroxylase and immunologically cross-reacting protein with termination of treatment in the aorta denotes values of 42 h for enzyme and 53 h for immunologically cross-reacting protein. Calculated enzyme κd values, by both methods, indicate that breakdown of enzyme does not account for tissue immunologically cross-reacting protein. 相似文献
16.
F Couraud H Rochat S Lissitzky 《Biochemical and biophysical research communications》1978,83(4):1525-1530
The protein neurotoxin II from the venom of the scorpion Hector was labeled with 125I by the lactoperoxidase method to a specific radioactivity of about 100 μCi/μg without loss of biological activity. The labeled neurotoxin binds specifically to a single class of non intereacting binding sites of high affinity (KD = 0.3 – 0.6 nM) and low capacity (4000 – 8000 sites/cell) to electrically excitable neuroblastoma cells. Relation of these sites to the action potential Na+ channel is derived from identical concentration dependence of scorpion toxin binding and increase in duration and amplitude of action potential. The protein neurotoxin II from the sea anemone also affects the closing of the action potential Na+ ionophore in nerve axons. The unlabelled sea anemone toxin modifies 125I-labeled scorpion toxin II binding to neuroblastoma cells by increasing the apparent KD for labeled scorpion toxin without modification of the number of binding sites. It is concluded that both scorpion toxin II and sea anemone toxin II interact competitively with a regulatory component of the action potential Na+ channel. 相似文献
17.
I.K. Adzamli R.A. Henderson H. Ong A.G. Sykes R. Cammack K.K. Rao 《Biochemical and biophysical research communications》1982,105(4):1582-1589
When parsley [2Fe-2S] and 2[4Fe-4S] proteins in the normal oxidised state are reduced 1:1 with Cr(II) (15-aneN4) (H2O)22+ the Cr(III) product remains attached to the protein and reduction is by an inner-sphere mechanism. With high potential [4Fe-4S] protein and rubredoxin the Cr(III) product is not attached to the protein and the mechanism is outer-sphere. Results are discussed in the context of protein crystallographic information. The Cr(III) product is not attached to the Fe2S2 core (extrusion experiments) or to the cysteinyl S-atoms (ESR). Negative patches close to the active site remain possible alternatives. 相似文献
18.
K J Kaufmann K M Petty P L Dutton P M Rentzepis 《Biochemical and biophysical research communications》1976,70(3):839-845
Following picosecond light activation, the bacteriochlorophyll and bacteriopheophytin complement of reaction centers depleted of ubiquinone behaves as though it has no primary electron acceptor; the excited intermediary state formed in <10 ps lasts >1 ns. Addition of ubiquinone-10 reconstitutes the very rapid electron transfer rates from the excited intermediary state to ubiquinone; the kinetics and rate are similar to that encountered in the untreated reaction centers. Interpretation of the data presented suggests that ubiquinone is the immediate electron acceptor from BPh?. This is consistent with the model for the primary reactions leading to [(BChl)2?BPh]Q?. 相似文献
19.
Male, weanling rats divided into three groups were maintained for 15 days on a semipurified diet containing either 5% casein fed (group 1), 20% casein pair-fed to group 1 (group 2), or 20% casein fed (group 3). Animals on day 16 were injected i.p. with 3H-AFB1 (1.90 mg/kg) and were sacrificed six hours later. In both the control and protein deficient animals, binding of AFB1 to DNA was greater than that for chromatin protein. In the protein deficient animals, there was a consistent decrease (70%) in binding to chromatin, DNA and chromatin protein. The decrease in binding to nuclear macromolecules in protein deficient animals is correlated with carcinogenicity and mixed function oxidase (MFO) enzyme activity, and the relationships between carcinogenicity, MFO activity, and binding are discussed. 相似文献
20.
Y Iwasa K Yonemitsu K Matsui K Fukunaga E Miyamoto 《Biochemical and biophysical research communications》1981,98(3):656-660
A heat-stable factor with properties similar to those of calmodulin was found in the fraction containing Ca2+-dependent cyclic AMP phosphodiesterase of . The factor activated such enzymes as cyclic nucleotide phosphodiesterase of bovine brain, (Ca2+,Mg2+)ATPase of human erythrocyte menbrane and myosin light chain kinase of rabbit myometrium in a Ca2+-dependent fashion with an apparent Ka of 5 × 10?5. The factor and brain calmodulin had no effect on the phosphodiesterase of . It may be concluded that calmodulin or a calmodulin-like protein occurs in prokaryotes. 相似文献