Showing papers on "Psychological repression published in 1972"
TL;DR: The synthesis of the bioluminescent system of the marine luminous bacterium Photobacterium fischeri (strain MAV) is subject to both transient and catabolite repression by glucose, and this repression can be reversed by adenosine 3':5'-cyclic monophosphate.
Abstract: The synthesis of the bioluminescent system of the marine luminous bacterium Photobacterium fischeri (strain MAV) is subject to both transient and catabolite repression by glucose, and this repression can be reversed by adenosine 3′:5′-cyclic monophosphate. Catabolite repression is a mechanism that characteristically controls the synthesis of inducible enzymes involved in energy metabolism. The fact that luciferase synthesis is subject to this control suggests that whatever its role(s) may be, it cannot be considered a nonfunctional or vestigial enzyme system as previously hypothesized, and may actually have some more direct role in metabolic processes.
72 citations
TL;DR: This work proposes that a glutamine-mediated modification of glutamine synthetase is responsible for repression of enzyme activity in Chinese hamster cells in tissue culture, indicating that protein synthesis (perhaps of new enzyme) is required for increased enzyme levels.
60 citations
TL;DR: Observations indicate that the functional holoenzyme of B 12 -transmethylase is essential for the repression by vitamin B 12 .
58 citations
TL;DR: The cI protein is an effective and specific repressor of RNA synthesis from the early gene region of λ DNA under optimal conditions and this repression is eliminated or severely impaired by the use ofλ DNA-carrying operator-type mutations which reduce the binding affinity of the cIprotein.
40 citations
Book•
01 Jan 1972
19 citations
TL;DR: It appears that the metE chemostat findings are peculiar to the phenotype of this mutant, which suggests a possible role for a functional methyltetrahydrofolate-homocysteine transmethylase in regulating the synthesis of the first enzyme.
Abstract: The regulation of the homocysteine branch of the methionine biosynthetic pathway in Salmonella typhimurium has been reexamined with the aid of a new assay for the first enzyme. The activity of this enzyme is subject to synergistic feedback inhibition by methionine plus S-adenosylmethionine. The synthesis of all three enzymes of the pathway is regulated by noncoordinate repression. The enzymes are derepressed in metJ and metK regulatory mutants, suggesting the existence of regulatory elements common to all three. Experiments with a methionine/vitamin B12 auxotroph (metE) grown in a chemostat on methionine or vitamin B12 suggested that the first enzyme is more sensitive to repression by methionine derived from exogenous than from endogenous sources. metB and metC mutants grown on methionine in the chemostat did not show hypersensitivity to repression by exogenous methionine. Therefore, it appears that the metE chemostat findings are peculiar to the phenotype of this mutant; such evidence suggests a possible role for a functional methyltetrahydrofolate-homocysteine transmethylase in regulating the synthesis of the first enzyme. Thus there appear to be regulatory elements which are common to the repression of all three enzymes, as well as some that are unique to the first enzyme. The nature of the corepressor is not known, but it may be a derivative of S-adenosylmethionine. metJ and metK mutants of Salmonella have a normal capacity for S-adenosylmethionine synthesis but may be blocked in synthesis or utilization of a corepressor derived from it.
18 citations
TL;DR: It has been postulated that either the repression of hepatic enzyme syntheses by glucose is independent of cyclic AMP levels or glucose indirectly interferes with the action of cycloheximide.
Abstract: THE synthesis of some liver enzymes can be repressed at translation by glucose1–3. Catabolic repression has been demonstrated for the Escherichia coli B-galactosidase system, in which glucose lowers the intracellular concentration of 3′ 5′ cyclic AMP4,5 required for the transcription of this particular mRNA6. In eukaryotes the evidence is more fragmentary: induction of liver tyrosine transaminase7, phospho-enol-pyruvate carboxykinase8–10, and serine dehydratase1,11 by glucagon is mediated by cyclic AMP. The synthesis of these and other enzymes can also be stimulated by cyclic AMP administration directly12. Cycloheximide inhibits the stimulation of all these enzyme syntheses while actinomycin D does not do so in all cases3,13–15. Addition of glucose can repress enzyme activity resulting from glucagon administration without lowering the elevated levels of cyclic AMP16–18. It has been postulated that either the repression of hepatic enzyme syntheses by glucose is independent of cyclic AMP levels or glucose indirectly interferes with the action of cyclic AMP16.
15 citations
13 citations
TL;DR: In this paper, the formation and decay of mRNA's corresponding to the argECBH genes of Escherichia coli have been studied by hybridization methods, and the transcriptional component was demonstrated in experiments (with rifampicin and 3H-uridine) on the completion of initiated mRNA's, under repression, derepression, or transitions between these control states.
11 citations
TL;DR: In this paper, two classes of partially virulent λCP mutants are identified: class I contains a mutation within the cI region which causes the modified cI product to negatively complement the active repressor present in the immune cells and class II achieve their virulence by a mutation which renders the x-y-cII-O operon insensitive to repression.
Abstract: Genetic studies coupled with functional analysis of gene action have demonstrated that there are two classes of partially virulent λCP mutants which differ in the mechanism by which they overcome the immunity repressor. Class I contains a mutation within the cI region which causes the modified cI product to negatively complement the active repressor present in the immune cells. Class II achieve their virulence by a mutation which renders the x-y-cII-O operon insensitive to repression.
10 citations
TL;DR: There is only one target site for catabolite repression in the lac operon, and it is found that a single alteration at the lac promoter region is sufficient to abolish sensitivity to repression of both cistrons.
Abstract: The catabolite repression caused by glucose and glucose-6-phosphate has been studied for both beta-galactosidase and thiogalactoside transacetylase, the products of the operator proximal and distal cistrons of the lac operon, respectively. We find that both cistrons are affected coordinately by this form of repression. We also find that a single alteration at the lac promoter region is sufficient to abolish sensitivity to repression of both cistrons. From this, we conclude that there is only one target site for catabolite repression in the lac operon.
TL;DR: A mutant with narrow repression-derepression range is concluded to have impaired translational repressibility and low transcriptional derepressibility of acetylornithinase, and evidence is provided that translational repression involves slowing of a phase such as initiation of translation, rather than peptide chain elongation.
01 Jan 1972
TL;DR: The data suggest that canavanine repression of thearginine pathway occurs only when high levels of canavanyl-tRNA are present, and the notion thatarginyl-t RNA synthetase plays a role inenerating a repression signal is supported.
Abstract: We showthatthearginine analogue, L-canavanine, repressed theaccumulationoftranslatable messengerribonucleic acid(RNA)forthree arginine biosynthetic enzymes inEscherichia coli. Themethodusedtodetermine thelevel of translatable messenger RNA depended upon measurement ofa burstofenzyme synthesis as described previously. E.coli strains withdefective arginyltransfer ribonucleic acid(tRNA)synthetase (argS mutants) were insensitive to canavanine repression. Whendeprived ofleucine, a leuargSstrain regained normalsensitivity tocanavanine repression. Thelevel ofinvivocanavanyltRNAarg was determined fora normal strain andan argSmutant. After 20min ofgrowth withcanavanine only9% oftRNAarg fromtheargSstrain was protected fromperiodate oxidation, while42%ofthetRNAargfroman argS+ strain was charged. Whendeprived ofleucine, leuargSor leuargS+strains grown withcanavanine contained more than60%charged tRNAarg. Reverse phasecolumnchromatography ofperiodate-oxidized tRNAfromcanavaninegrown argSandargS+strains showed no preferential charging ofany isoaccepting species oftRNAarg. Therefore, we failed todetect a specific arginyltRNAspecies thatmightbeinvolved inrepression bycanavanine. However, thedatasuggest thatcanavanine repression ofthearginine pathway occurs onlywhenhighlevels ofcanavanyl-tRNA are present, andthussupportthe notion thatarginyl-tRNA synthetase plays a roleingenerating a repression signal.
01 Jan 1972