The ilvG gene is expressed in Escherichia coli K-12

Berg, Claire M.; Shaw, Karen Joy; Berg, Douglas E.

doi:10.1016/0378-1119(80)90028-1

Cited by 19 publications

(16 citation statements)

References 23 publications

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“…All these AHAS isozymes catalyze the first step of the last four common steps in isoleucine and valine biosyntheses and are sensitive to feedback inhibition by valine (Guardiola et al 1977;Berg et al 1980). The synthesis of the three AHAS isozymes are regulated differently (Umbarger,1978); i.e., the synthesis of AHAS I is multivalently controlled by leucine and valine, that of AHAS II by isoleucine, leucine, and valine, and that of AHAS III by leucine alone.…”

Section: Introductionmentioning

confidence: 99%

“…1, E. coli K12 was found to contain three isozymes of acetohydroxy acid synthase (AHAS) (EC 4.1.3.18, acetolactate synthase) ; AH AS I, AHAS II and AHAS III (Guardiola et al 1974; De Felice et at. 1978a, b) coded by the structural genes ilvB, ilvG and ilvHI, respectively.All these AHAS isozymes catalyze the first step of the last four common steps in isoleucine and valine biosyntheses and are sensitive to feedback inhibition by valine (Guardiola et al 1977;Berg et al 1980). The synthesis of the three AHAS isozymes are regulated differently (Umbarger,1978); i.e., the synthesis of AHAS I is multivalently controlled by leucine and valine, that of AHAS II by isoleucine, leucine, and valine, and that of AHAS III by leucine alone.…”

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confidence: 99%

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Regulation of the ilv operon in Escherichia coli K-12. Roles of threonine and isoleucine.

Okada

1983

The Japanese journal of genetics

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Under the shift-down condition, threonine, a-ketobutyrate and isoleucine at certain concentrations derepressed the synthesis of acetohydroxy acid synthase and isomeroreductase but did not derepress that of transaminase B or threonine deaminase in Escherichia coli W3110-215.Leucine and/or valine counteracted the derepressing effect of isoleucine on the synthesis of acetohydroxy acid synthase and isomeroreductase. Leucine and valine in the absence of isoleucine completely inhibited derepression of the synthesis of these enzymes after shift-down. These results suggested that isoleucine at a certain concentration is possibly necessary for the efficient derepression of the synthesis of acetohydroxy acid synthase I coded by the ilvB gene and/or acetohydroxy acid synthase III coded by the ilvHI gene.The model for regulation of ilv operon in Escherichia coli and Salmonella typhimurium was first proposed by Hatfield and Burns (1970) and then extended by Calhoun and Hatfield (1973). The latter model is now modified as shown in Fig. 1. The rho factor and intercistronic promoters (Smith et al. 1976;Berg and Shaw 1981) are omitted from this model for simplicity.As shown in Fig. 1, E. coli K12 was found to contain three isozymes of acetohydroxy acid synthase (AHAS) (EC 4.1.3.18, acetolactate synthase) ; AH AS I, AHAS II and AHAS III (Guardiola et al 1974; De Felice et at. 1978a, b) coded by the structural genes ilvB, ilvG and ilvHI, respectively.All these AHAS isozymes catalyze the first step of the last four common steps in isoleucine and valine biosyntheses and are sensitive to feedback inhibition by valine (Guardiola et al. 1977;Berg et al. 1980). The synthesis of the three AHAS isozymes are regulated differently (Umbarger,1978); i.e., the synthesis of AHAS I is multivalently controlled by leucine and valine, that of AHAS II by isoleucine, leucine, and valine, and that of AHAS III by leucine alone. Therefore, isoleucine has been believed to be involved solely in the control of 1) This study was supported in part by a Grant-in-Aid for Cooperative Research from the Ministry of Education, Science and Culture of Japan. 60Toshihiko OKADA synthesis of AHAS II. However, Wiginton and Shive (1978) found that, under the shift-down condition, addition of isoleucine in the absence of valine and leucine repressed the synthesis of valr AHAS and derepressed that of vals AHAS.The organism employed in this study was W3110-215 (A-F-thy-deoC-) derived from W3110 (AF) (Okada et al. 1969) . Cells in the exponential phase of growth in nutrient broth were washed and transferred to minimal medium supplemented with 10 pg of thymine per ml for growth of the strain and with various compounds indicated in each table. Growth of cells was followed Aporepressors are supposed to interact with free leucine, valine and/or isoleucine to form holo-repressors that repress expression of the ilvHI, ilvB and/or i1vOGEDA operons. The isoleucyl-, leucyl, and valyl-tRNAs interact with leader RNA produced from the attenuator region of the i1vOGEDA oper...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Regulation of the ilv operon in Escherichia coli K-12. Roles of threonine and isoleucine.

Okada

1983

The Japanese journal of genetics

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“…Expression of ilvB is multivalently controlled by leucine and valine (De Felice et al 1978a), that of ilvG in the ilvOGEDA operon (Berg et al 1979(Berg et al , 1980Subrahmanyam et al 1980;Lawther and Hatfield 1980) by isoleucine, leucine and valine (Lawther and Hatfield 1978) and that of ilvHI by leucine alone (De Felice and Levinthal 1977). Therefore, limitation of leucine derepresses the syntheses of AHAS I, AHAS II and AHAS III and that of valine derepresses the syntheses of AHAS I and AHAS II.…”

Section: Discussionmentioning

confidence: 99%

“…However, ilvR may be a real regulatory region, first because transcription of ilvG has been demonstrated in ilv0+ strains of E. coli K12 (Subrahmanyam et a1.1980) and second because the i1vEDA and ilvC genes which are flanking on each other, and possibly the ilvG gene also, are all transcribed in a clockwise direction (Cohen and Jones 1976;Smith et al 1976;Childs et al 1977;McCorkle et al 1978;Baez et al 1979). Berg et al (1980) recently reported that the ilvG gene product, AHAS II, is indeed produced in ilv0~ strains of E. colt K12, and that, contrary to previous reports, AHAS II is sensitive to feedback inhibition by valine. They suggested that ilvO mutations are within ilvG and pleiotropic in that they alter the valine-binding site of AHAS II insensitive to valineinhibition and increase transcription of downstream genes, ilvE, D and A.…”

Section: Introductionmentioning

confidence: 99%

“…They suggested that ilvO mutations are within ilvG and pleiotropic in that they alter the valine-binding site of AHAS II insensitive to valineinhibition and increase transcription of downstream genes, ilvE, D and A. They also suggested that the AHAS isozymes act in a complex (Berg et al 1980). If this is the case, AHAS activity in a crude extract of E. coli K12 could be a total activity of the complex.…”

Section: Introductionmentioning

confidence: 99%

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Derepression of valine-sensitive acetohydroxy acid synthase by threonine, .ALPHA.-ketobutyrate or isoleucine in Escherichia coli K12.

Okada

1982

The Japanese journal of genetics

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After nutritional shift-down, threonine, a-ketobutyrate, or isoleucine within certain concentration range stimulated derepression of the synthesis of acetohydroxy acid synthase in strain W3110-215, a low-thymine requiring derivative of Escherichia coli K12. The acetohydroxy acid synthase induced by isoleucine was valine-sensitive.Since chloramphenicol inhibited the increase of the enzyme activity, the increase seemed to be due to enhancement of enzyme synthesis and not to the activation of the enzyme. From these results, it was suggested that not only limitation of leucine or valine, but also the presence of excess threonine or isoleucine is necessary for efficient derepression of the synthesis of acetohydroxy acid synthase.On the other hand, threonine did not stimulate the derepression of the synthesis of the enzyme in strains W2252 and 58-161, methionine-auxotrophic mutants of E. coli K12, growing in minimal medium containing methionine. When a prototrophic strain with regard to methionine requirement was used, methionine or threonine added in minimal medium derepressed synthesis of acetohydroxy acid synthase, but the simultaneous addition of the two compounds did not give any synergistic effect on the enzyme synthesis. The mechanisms of these phenomena are unknown.

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Genetical and structural analysis of a group of λilv and λrho transducing phages

et al. 1981

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Eight lambda ilv C transducing phages generated from E. coli K12 secondary site lysogens have been analysed genetically and physically. Two of them carry, in addition, the rho gene and its promotor region, but not the cya gene. The ilv O 603 mutation has been located between ilv G and ilv E. Electrophoretic analysis of the proteins synthesized by these phages in a system of UV irradiated cells allowed us to assign molecular weights of 55000 and 66000 daltons to the ilv C and the ilv D gene products, respectively, and to show that an ilv G-encoded polypeptide of 60000 daltons is made from an ilv O- but not from an ilv O+ phage. The expression of the ilv G gene is discussed in the light of the recent finding of a promoter-attenuator region lying upstream to ilv G. Finally, we have found that one of the lambda ilv phages does not have the classical structure of a transducing phage.

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The ilvG gene is expressed in Escherichia coli K-12

Cited by 19 publications

References 23 publications

Regulation of the ilv operon in Escherichia coli K-12. Roles of threonine and isoleucine.

Regulation of the ilv operon in Escherichia coli K-12. Roles of threonine and isoleucine.

Derepression of valine-sensitive acetohydroxy acid synthase by threonine, .ALPHA.-ketobutyrate or isoleucine in Escherichia coli K12.

Genetical and structural analysis of a group of λilv and λrho transducing phages

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