1. An ATPase complex containing 12 subunits was isoalted from rat liver mitochondria. 2. In vivo inhibition of mitochondrial protein synthesis by the chloramphenicol analogue thiamphenicol leads to the formation of an...
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1. An ATPase complex containing 12 subunits was isoalted from rat liver mitochondria. 2. In vivo inhibition of mitochondrial protein synthesis by the chloramphenicol analogue thiamphenicol leads to the formation of an oligomycin-insensitive membrane-bound ATPase complex in mitochondria of regenerating rat liver. 3. This oligomycin-insensitive, membrane-bound ATPase was isolated by the same procedure as the ATPase complex from regenerating livers of untreated animals. 4. SDS-polyacrylamide gel electrophoresis of in vivo labelled ATPase complexes from control and from thiamphenicol-treated rats reveals that three subunits out of the 12 are not synthesized or assembled when the mitochondrial translation activity is blocked. 5. from the subunits synthesized and assembled when mitochondrial pror (fo) of the ATPase complex (subunit 5). 6. The oligomycin sensitivity-conferring protein seems absent in the ATPase complex formed in the presence of thiamphenicol.
The hydroxylapatite-column assay of estrogen receptors, described previously [Erdos et al. Analyt. Biochem. 37 244 (1970)], has been modified for the routine analyses of many samples. Sixty assays can be performed in ...
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The primary reactions of the neutral and protonated riboflavin triplet states with phenylacetic acid, indole-acetic acid and several similar derivatives have been examined by laser flash photolysis. The results indica...
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The primary reactions of the neutral and protonated riboflavin triplet states with phenylacetic acid, indole-acetic acid and several similar derivatives have been examined by laser flash photolysis. The results indicate that one-electron transfer to the flavin triplet state(s) is the major reaction of all the substrates studied, two electron processes (group transfer) are not significant. The observed difference in reactivity of each substrate with the neutral and protonated triplet states is discussed in terms of the pH dependence of photoreduction, previously reported in the literature.
The fate of artifacts incorporated into the ploughsoil as a result of plough damage is considered in terms of two soil mark sites near Winchester, Hampshire. Ploughsoil and subsoil analyses indicate that dispersal of ...
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The fate of artifacts incorporated into the ploughsoil as a result of plough damage is considered in terms of two soil mark sites near Winchester, Hampshire. Ploughsoil and subsoil analyses indicate that dispersal of soil material, as a result of ploughing, is limited at the present time and under mould board ploughing techniques. The origin of soil marks underlain only by bedrock is also considered and evidence indicates that such soil marks may appear as groundsurface expressions of ditches which have been removed by plough damage where dispersal of ploughsoil is minimal. Such soil marks may be only short lived if plough depth continues to increase.
Protein synthesis in reticulocytes and their lysates is regulated by heme. In heme deficiency a heme-regulated translational inhibitor (HRI) that blocks initiation of polypeptide chains is activated. HRI is a protein ...
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Protein synthesis in reticulocytes and their lysates is regulated by heme. In heme deficiency a heme-regulated translational inhibitor (HRI) that blocks initiation of polypeptide chains is activated. HRI is a protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) that specifically phosphorylates the 38,000 dalton subunit of the Met-tRNAfMet binding factor (If), which forms a ternary complex with Met-tRNAfMet and GTP, a finding that suggests that the inhibition by HRI involves the phosphorylation of If. The effect of HRI in the partial reactions of protein chain initiation in which the If-promoted binding of Met-tRNAfMet to 40S ribosomal subunits is enhanced by another initiation factor [ternary complex dissociation factor (TDf)] and AUG was investigated HRI at very low concentrations markedly inhibits the bindings of Met-tRNAfMet to 40S subunits. The inhibitory effect of HRI requires ATP. Under these conditions HRI phosphorylates only the 38,000 dalton subunit of If The TDf preparations not only promote the binding of the ternary complex to 40S subunits but also promote the dissociation of the ternary complex in the presence of 5 mM Mg2+ at ***. C. The preincubation of purified If alone with low concentrations of HRI and ATP does not significantly affect its capacity to form the ternary complex;however, the TDf-promoted dissociation of the ternary complex is inhibited. The nonhydrolyzable analog adenosine 5''[.beta..gamma.-imido]triphosphate does not substitute for ATP. Phosphorylation apparently causes a conformational modification in If, which results in inhibition of the interaction between the ternary complex and TDf that is required for the binding of the ternary complex to 40S subunits.
The site of biosynthesis of transformylase, an enzyme of plastid and mitochondrial protein synthesizing system, was studied in autotrophic and heterotrophic E. gracilis cells. In light-grown cells and in resting dark-...
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The site of biosynthesis of transformylase, an enzyme of plastid and mitochondrial protein synthesizing system, was studied in autotrophic and heterotrophic E. gracilis cells. In light-grown cells and in resting dark-grown cells cultivated in light, chloramphenicol (CAP) didn''t modify the level of transformylase activity. The enzyme from dark-grown cells was unaffected by the addition of ethidium bromide to the medium, whereas transformylase accumulation was stimulated by addition of CAP. Apparently both plastidial and mitochondrial transformylase are synthesized on cytoplasmic ribosomes. A regulation mechanism for the etioplast transformylase is proposed.
The antihypertensive effects of trans-4-methyl-7,8-dihydroxy-1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinoline, a dopamine agonist, were investigated in dogs and spontaneous hypertensive rats. I.v. administration of low d...
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The antihypertensive effects of trans-4-methyl-7,8-dihydroxy-1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinoline, a dopamine agonist, were investigated in dogs and spontaneous hypertensive rats. I.v. administration of low doses of this cyclic analog of dopamine (0.25-1.00 .mu.g/kg) consistently reduced blood pressure and heart rate, concurrently recorded in the dog. This effect was antagonized by haloperidol, a specific dopamine antagonist. The dopamine analog also reduced systolic blood pressure of spontaneous hypertensive rats. The possibility that the decrease in blood pressure and heart rate elicited by the dopamine analog is attributable to an effect on specific dopaminergic receptors is confirmed.
8-Azido-ATP is a substrate for E. coli (Ca2+ + Mg2+)-ATPase (E. coli f1). Illumination of E. coli f1 in the presence of 8-azido-ATP causes inhibition of ATPase activity. The presence of ATP during illumination prevent...
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8-Azido-ATP is a substrate for E. coli (Ca2+ + Mg2+)-ATPase (E. coli f1). Illumination of E. coli f1 in the presence of 8-azido-ATP causes inhibition of ATPase activity. The presence of ATP during illumination prevents inhibition. 8-Azido-ATP and 4-chloro-7-nitrobenzofurazan (NbfCl) bind predominantly to the .alpha. subunit of the enzyme, but also significantly to the .beta. subunit. The .alpha. subunit of E. coli f1 had some properties that in other f11-ATPases are associated with the .beta. subunit.
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