Showing papers on "Psychological repression published in 1973"
TL;DR: By growing in parallel a mutant strain with temperature-sensitive repressor and an isogenic control with a deletion in the regulator gene at progressively higher temperatures, it was possible to show that respiratory repression most likely involves a third mechanism of control, independent of specific or catabolite repression.
Abstract: Three kinds of control mechanisms govern the expression of the members of the glp regulon for glycerol and sn-glycerol 3-phosphate (G3P) catabolism in Escherichia coli K-12: specific repression by the product of the glpR gene; catabolite repression; and respiratory repression (the effect exerted by exogenous hydrogen acceptors). The operons of the glp system show different patterns of response to each control. By growing in parallel a mutant strain with temperature-sensitive repressor (glpRts) and an isogenic control with a deletion in the regulator gene at progressively higher temperatures, it was possible to show that the synthesis of aerobic G3P dehydrogenase (glpD product) is far more sensitive to specific repression than that of either glycerol kinase (glpK product) or G3P transport (glpT product). Conversely, in the strain with a deletion in the regulator gene, the syntheses of glycerol kinase and G3P transport are more sensitive to catabolite repression than that of the aerobic G3P dehydrogenase. The levels of the two flavoprotein G3P dehydrogenases vary in opposite directions in response to changes of exogenous hydrogen acceptors. For example, the ratio of the aerobic enzyme to the anaerobic enzyme (specified by glpA) is high when molecular oxygen or nitrate serves as the hydrogen acceptor and low when fumarate plays this role. This trend is not influenced by the addition of cyclic adenosine 3′,5′-monophosphate to the growth medium. Thus, respiratory repression most likely involves a third mechanism of control, independent of specific or catabolite repression.
84 citations
TL;DR: Evidence is presented to indicate that 5-methyltetrahydrofolate-homocysteine methyl transferase (“B12 transmethylase”) is an inducible enzyme.
59 citations
TL;DR: The autoregulatory model is presented in an expanded form to include recent evidence that L-threonine deaminase is a central element for repression of the ilvADE and ilvB operons, and for induction of theIlvC operon.
Abstract: It was previously proposed, primarily on the basis of evidence in vitro, that L-threonine deaminase, the ilvA gene product, is required for repression of its own synthesis and for repression of the other genes in the ilv-ADE operon. In this communication, evidence in vivo is presented that supports this autoregulatory model. Further evidence is presented that suggests that L-threonine deaminase is also required for induction of the ilvC gene product. The autoregulatory model is presented in an expanded form to include recent evidence that L-threonine deaminase (EC 4.2.1.16) is a central element for repression of the ilvADE and ilvB operons, and for induction of the ilvC operon.
42 citations
TL;DR: The dsdC strains were found to be much more sensitive to induction by d-serine than are dSDC(+) strains under conditions of catabolite repression, which suggests that a d-Serine-dsdC complex may be able to replace partially the cyAMP:cyAMP-binding protein action in initiation of Dsdase messenger ribonucleic acid synthesis-a positive control effect.
Abstract: Adenosine 3',5'-cyclic monophosphate (cyAMP) and the cyAMP-binding protein are necessary for efficient induction of d-serine deaminase (Dsdase) synthesis in dsdC(+)dsdO(+) and dsdC dsdO(+) strains of Escherichia coli K-12, and for constitutive synthesis in dsdC dsdO(+) strains. Neither is required in dsdO strains, confirming previous indications that in dsdO mutants Dsdase synthesis is not subject to catabolite repression control. Since efficient Dsdase synthesis in dsdC(+) and dsdC strains that are dsdO(+) requires the cyAMP-binding protein, which acts at the level of transcription in other systems, it is concluded that catabolite repression acts at the level of transcription of the Dsdase structural gene. Since catabolite repression is reversed by the inducer, d-serine in dsdC dsdO(+) strains, it is concluded that induction also acts at the level of transcription in this system. The dsdC strains were found to be much more sensitive to induction by d-serine than are dsdC(+) strains under conditions of catabolite repression, whether the repression was caused by glucose or by loss of ability to form cyAMP or cyAMP-binding protein. This suggests that a d-serine-dsdC complex may be able to replace partially the cyAMP:cyAMP-binding protein action in initiation of Dsdase messenger ribonucleic acid synthesis-a positive control effect.
33 citations
TL;DR: Development of a system for in vitro synthesis of N-α-acetyl-L-ornithinase of E. coli has made it possible to detect the argR gene product, i.e., the arginine repressor, in cell extracts.
Abstract: Development of a system for in vitro synthesis of N-α-acetyl-L-ornithinase of E coli has made it possible to detect the argR gene product, ie, the arginine repressor, in cell extracts
32 citations
TL;DR: The in vitro repression of transcription of the tryptophan operon by the trp repressor from Escherichia coli was studied and the repression or derepression was similar to that observed in vivo.
Abstract: The in vitro repression of transcription of the tryptophan operon by the trp repressor from Escherichia coli was studied. By measuring the inhibitory effect for trp-specific RNA synthesis in an in vitro transcription system directed by DNA of trp-transducing phage, we have detected and concentrated a trp repressor in an eluate of a Φ80 ptED native DNA-cellulose column. The repression of transcription of trp operon required the addition of L-tryptophan in the system, and when several tryptophan analogues were added, the repression or derepression was similar to that observed in vivo. The repressor fraction was separated from the majority of tryptophanyl-tRNA synthetase activity by Bio-gel P60 column chromatography.
29 citations
TL;DR: It is tentatively concluded that intact threonine deaminase is required for derepression by two of the effectors for multivalent repression, but not by the third, and a model is presented which proposes that a regulatory species of leu tRNA(leu) is the key intermediate for repression and that threonines deaminases is a positive element, regulating the available pool of charged leuTRNA by binding it.
Abstract: l-Threonine deaminase (l-threonine dehydratase [deaminating], EC 4.2.2.16) has been shown to be involved in the regulation of three of the enzymes of isoleucine-valine biosynthesis in yeast. Mutations affecting the affinity of the enzyme for isoleucine also affected the repression of acetohydroxyacid synthase, dihydroxyacid dehydrase, and reductoisomerase. The data indicate that isoleucine must be bound for effective repression of these enzymes to take place. In a strain with a nonsense mutation midway in liv 1, the gene for threonine deaminase, starvation for isoleucine or valine did not lead to derepression of the three enzymes; starvation for leucine did. The effect of the nonsense mutation is recessive; it is tentatively concluded, therefore, that intact threonine deaminase is required for derepression by two of the effectors for multivalent repression, but not by the third. A model is presented which proposes that a regulatory species of leu tRNA(leu) is the key intermediate for repression and that threonine deaminase is a positive element, regulating the available pool of charged leu tRNA by binding it.
25 citations
TL;DR: It is found that a cytidine compound is the primary effector of repression in all cases except for aspartate transcarbamylase where little repression is observed in excess cytidine.
Abstract: It has been reported by other workers that a uridine and probably also a cytidine nucleotide are required for maximal repression of aspartate transcarbamylase encoded by the gene pyrB in Salmonella typhimurium. We have identified the repressing metabolites for three more biosynthetic enzymes, namely, dihydroorotate dehydrogenase (encoded by pyrD), orotidine-5′-monophosphate pyrophosphorylase (encoded by pyrE), and orotidine-5′-monophosphate decarboxylase (encoded by pyrF), as well as examining the repression profiles of aspartate transcarbamylase in more detail. Using a specially constructed strain of S. typhimurium (JL1055) which lacks the enzymes for the interconversion of cytidine and uridine compounds, thus allowing the independent manipulation of endogenous cytidine and uridine nucleotides, we found that a cytidine compound is the primary effector of repression in all cases except for aspartate transcarbamylase where little repression is observed in excess cytidine. For aspartate transcarbamylase, we found that the primary repressing metabolite is a uridine compound.
23 citations
TL;DR: Starvation of a pdx mutant of Escherichia coli strain B in the presence of repressing levels of isoleucine, valine and leucine leads to a derepression of the normally repressible ilv genes.
18 citations
TL;DR: The synthesis of two enzymes of the arginine catabolic pathway, arginase and ornithine δ-transaminase, in Aspergillus nidulans was found to be sensitive to both glucose and ammonium repression.
Abstract: The synthesis of two enzymes of the arginine catabolic pathway, arginase and ornithine δ-transaminase (OTAse), in Aspergillus nidulans was found to be sensitive to both glucose and ammonium repression. The glucose and nitrogen starvation result in the identical derepression of OTAse synthesis and have no effects on arginase synthesis. Glucose and ammonium affect the kinetics of induction of both enzymes, however, the effect of ammonium is much stronger. Evidence was obtained for the direct involvement of ammonium in the repression phenomenon. The relations between glucose and ammonium repression are discussed.
17 citations
TL;DR: In this article, a mutation, amdT19, which leads to inability to grow on glutamate as the sole nitrogen source but does not affect growth on glutamate, is shown to result in increased repression of glutamate uptake by glucose.
TL;DR: Results reported here show that the repressive action of glutamine on sporulation described previously is brought about by those early steps of the purine nucleotide pathway in which glutamine is an amino group donor.
TL;DR: The leucine analogue 4-azaleucine was found to replaceLeucine in multivalent repression of threonine deaminase-forming potential in Escherichia coli but not in Salmonella typhimurium.
Abstract: Two isoleucine analogues and two leucine analogues were examined for their ability to replace the natural amino acid preventing the accumulation of threonine deaminase-forming potential. The procedure used to study repression by the analogues distinguishes between true repression and the formation of inactive enzyme by the analogue in question. The leucine analogue 4-azaleucine was found to replace leucine in multivalent repression of threonine deaminase-forming potential in Escherichia coli but not in Salmonella typhimurium. Another leucine analogue, trifluoroleucine, was only partially effective in causing repression in either organism. The isoleucine analogue 4-azaisoleucine was ineffective in replacing isoleucine in repression. In contrast, 4-thiaisoleucine effectively replaced isoleucine in the repression of threonine deaminase-forming potential in S. typhimurium and E. coli.
TL;DR: Two kinds of mutants of Aspergillus nidulans with altered response of arginine catabolic enzymes to glucose and ammonium repression were obtained, both of which are recessive while AniA are dominant.
Abstract: Two kinds of mutants of Aspergillus nidulans with altered response of arginine catabolic enzymes to glucose and ammonium repression were obtained Mutations in the suF locus result in the insensitivity of these enzymes to glucose and to one type of ammonium repression Mutations in the AniA locus result in hypersensitivity to both types of repression The enzymes studied can be induced by arginine in AniA mutants only when glucose or the nitrogen source is removed from the medium The suF mutations are recessive while AniA are dominant Double suF AniA mutants retain only the suF properties The functions of both genes and their interrelations are discussed
01 Jan 1973
01 Jan 1973
TL;DR: It is shown that thesynthesis ofaerobic G3Pdehydrogenase (glpD product) is more sensitive to specific repression than that of either glycerol kinase(glpKproduct) orG3Ptransport (glPT product), and respiratory repression most likely involves a thirdmechanism ofcontrol, independent of specific orcatabolite repression.
Abstract: Threekindsofcontrol mechanisms governtheexpression ofthemembersof theglpregulon forglycerol andsn-glycerol 3-phosphate (G3P)catabolism in Escherichia coliK-12:specific repression bytheproduct oftheglpRgene; catabolite repression; andrespiratory repression (the effect exerted byexogenous hydrogen acceptors). Theoperonsoftheglpsystemshowdifferent patterns of responsetoeachcontrol. Bygrowing inparallel a mutantstrain withtemperature-sensitive repressor(glpRt8) andan isogenic control witha deletion inthe regulator geneatprogressively higher temperatures, itwas possible toshowthat thesynthesis ofaerobic G3Pdehydrogenase (glpD product) isfarmore sensitive to specific repression thanthatofeither glycerol kinase(glpKproduct) orG3Ptransport (glpT product). Conversely, inthestrain withadeletion inthe regulator gene,thesyntheses ofglycerol kinase andG3Ptransport are more sensitive tocatabolite repression thanthatoftheaerobic G3Pdehydrogenase. The levels ofthetwo flavoprotein G3P dehydrogenases vary inopposite directions inresponsetochanges ofexogenoushydrogen acceptors. Forexample, theratio oftheaerobic enzyme totheanaerobic enzyme (specified bygipA) is highwhenmolecular oxygenornitrate servesasthehydrogen acceptor andlow whenfumarate plays thisrole. Thistrendisnotinfluenced bytheaddition of cyclic adenosine 3', 5'-monophosphate tothegrowth medium.Thus,respiratory repression mostlikely involves a thirdmechanism ofcontrol, independent of specific orcatabolite repression.