Regulation of the Salmonella typhimurium metA gene by the metR protein and homocysteine

Mares, Rosa E.; Urbanowski, Mark L.; Stauffer, George V.

doi:10.1128/jb.174.2.390-397.1992

Cited by 43 publications

(33 citation statements)

References 28 publications

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“…MetR by itself activates metH expression (Urbanowski & Stauffer, 1989a;, and a MetR-homocysteine complex in the absence of the MetJ-SAM repressor is needed for efficient expression of metE (Plamann et al, 1988;. In addition, MetR -cells are impaired to some degree in expression of metA and metF, each of which is downregulated when homocysteine levels increase, a result presumably of increased levels of the MetR-homocysteine complex and a concomitant decrease of the free MetR activator protein in the cell (Cowen et al, 1993;Mares et al, 1992). It is also possible that MetR, free or bound to homocysteine, is needed in some way for efficient expression of other met genes.…”

Section: Discussionmentioning

confidence: 99%

“…As described by Mulligan et al (1982), the GW strains were identified by screening for defects in methionine metabolism after Mud : : Ap,lac-mediated insertional mutagenesis of BW545, and the metJ : : Tn5 and metK : : Tn5 markers were inserted into the originally identified and stabilized met reporter strains by P1 vir transduction. BWmJ and BWmK are metJ : : Tn5 and metK : : Tn5 derivatives of BW545 produced by P1 vir transduction (Mares et al, 1992) of the respective markers from GW2529 and GW2533. They were identified by screening for resistance to 50 mg kanamycin ml 21 on YT agar plates after P1 vir transduction and subsequent demonstration of elevated MetC activity using the assay described below.…”

Section: Methodsmentioning

confidence: 99%

“…We deemed the use of met wild-type cells to be especially important. For example, defects in homocysteine biosynthesis in MetA -strains or in its use in MetE -or MetF -strains would likely alter MetR-mediated gene activation (Byerly et al, 1990;Cowen et al, 1993;Mares et al, 1992; and introduce complex and unpredictable effects beyond those provoked by SAMase expression.…”

Section: Effect Of In Vivo Samase Expression In Met Wild-type Cells Imentioning

confidence: 99%

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In vivo hydrolysis of S-adenosylmethionine induces the met regulon of Escherichia coli

LaMonte

Hughes

2006

Microbiology

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Regulation of methionine biosynthesis in Escherichia coli involves a complex of the MetJ aporepressor protein and S-adenosylmethionine (SAM) repressing expression of most genes in the met regulon. To test the role of SAM in the regulation of met genes directly, SAM pools were depleted by the in vivo expression of the cloned plasmid vector-based coliphage T3 SAM hydrolase (SAMase) gene. Cultures with in vivo SAMase activity were assayed for expression of the metA, B, C, E, F, H, J, K and R genes in cells grown in methionine-rich complete media as well as in defined media with and without L-methionine. In vivo SAMase activity dramatically induced expression between 11-and nearly 1000-fold depending on the gene assayed for all but metJ and metH, and these genes were induced over twofold. metJ : : Tn5 (aporepressor defective) and metK : : Tn5 (SAM synthetase impaired; produces <5 % of wild-type SAM) strains containing in vivo SAMase activity produced even higher met gene activity than that seen in comparably prepared cells with wild-type genes for all but metJ in a MetJ-deficient background. The SAMasemediated hyperinduction of metH in wild-type cells and of the met genes assayed in metJ : : Tn5 and metK : : Tn5 cells provokes questions about how other elements such as the MetR activator protein or factors beyond the met regulon itself might be involved in the regulation of genes responsible for methionine biosynthesis.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Effect Of In Vivo Samase Expression In Met Wild-type Cells Imentioning

confidence: 99%

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In vivo hydrolysis of S-adenosylmethionine induces the met regulon of Escherichia coli

LaMonte

Hughes

2006

Microbiology

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“…The absence of a specific promoter for Leptospira metX and the absence of regulation at the enzymatic level are in contrast to the multiple regulation of expression of the E. coli metA gene by MetJ, MetR, and 32 and feedback inhibition of O-succinyltransferase by methionine plus S-adenosylmethionine (2,14,19). Though feedback inhibition does not take place for MetX, it was found for the second enzyme (MetY) of the Leptospira methionine pathway (1).…”

mentioning

confidence: 92%

Homoserine O-acetyltransferase, involved in the Leptospira meyeri methionine biosynthetic pathway, is not feedback inhibited

et al. 1997

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The Leptospira meyeri serovar semaranga metX gene was identified by complementation of an Escherichia coli metA mutant, i.e., devoid of homoserine O-succinyltransferase. However, the MetX protein exhibited a homoserine O-acetyltransferase activity in agreement with its similarity to homoserine O-acetyltransferases. Reverse transcription-PCR analysis demonstrated that metX is the second gene of an operon.The first step of the biosynthetic pathway leading to methionine is esterification of homoserine (6). However, the precursor differs according to the organism. In members of the family Enterobacteriaceae, O-succinyl-homoserine is formed by acylation of homoserine in the presence of O-succinyl-coenzyme A, catalyzed by homoserine O-succinyltransferase, the metA gene product (7,18). In gram-positive bacteria of the genus Bacillus and in fungi, esterification of homoserine occurs by an acetylation (3, 9, 13) catalyzed by a homoserine O-acetyltransferase.The genus Leptospira consists of two nomenspecies, Leptospira interrogans sensu lato (pathogenic) and Leptospira biflexa sensu lato (nonpathogenic), which belong to the order Spirochaetales (4). Previous studies indicated that Leptospira spp. synthesize most of their amino acids by the same biosynthetic pathways as those used by Escherichia coli (5).Our interest in methionine biosynthesis in Leptospira arose from the fact that radiotracer studies of biosynthetic pathways did not include any data for the methionine pathway (5). In this paper, we describe isolation and transcriptional organization of the metX gene, as well as the enzymatic characterization and regulation of its product, homoserine O-acetyltransferase.(This work represents a portion of a thesis submitted by P. Bourhy to the University of Paris VII, Paris, France, for the Ph.D.)Cloning of a DNA fragment from Leptospira meyeri which can complement an E. coli metA mutant. We had previously constructed a recombinant cosmid library and cloned the Leptospira metY gene, which complemented E. coli metB mutants (1). The size of the cloned DNA fragment (25 kbp) in the pb10 recombinant cosmid suggested that other methionine biosynthetic genes might be found on this fragment. In order to test this hypothesis, E. coli RC709 (metF63 pro-22; R. Clowes) and AB1932 (metA28 argH1 thi-1 lacY1 lacZ4 galK2 xyl-4 [or -5] tsx-6 F Ϫ ; E. A. Adelberg) were used for complementation experiments in supplemented M9 minimal medium (20) at 30°C. Both strains were electroporated with pb10. pb10 weakly complemented metA but not metF mutants. Further subcloning experiments allowed us to locate the Leptospira DNA able to complement E. coli metA and metB mutants more precisely within a 6.8-kbp fragment. Plasmid pb12 carrying a 6.8-kbp PstI fragment from pb10 in the pBR322 vector (22) still complemented E. coli metB and metA mutants (Fig.

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“…The met regulon genes, except metH, are under negative transcriptional control of the MetJ repressor, with S-adenosylmethionine as a corepressor (Saint-Girons et al, 1988). In addition to MetJmediated negative control the metE, metA, metF, metH and glyA genes are under positive control of the MetR activator (Cowan et al, 1993;Lorenz & Stauffer, 1996;Mares et al, 1992;Maxon et al, 1989;Urbanowski & Stauffer, 1989;Weissbach & Brot, 1991).…”

Section: Introductionmentioning

confidence: 99%

Molecular characterization of the CmbR activator-binding site in the metC–cysK promoter region in Lactococcus lactis

et al. 2005

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The metC-cysK operon involved in sulphur metabolism in Lactococcus lactis is positively regulated by the LysR-type protein CmbR. Transcription from the metC promoter is activated when concentrations of methionine and cysteine in the growth medium are low. The metC promoter region contains two direct and three inverted repeats. Deletion analysis indicated that direct repeat 2 (DR2) is required for activation of the metC promoter by CmbR. Gel mobility shift assays confirmed that CmbR binds to a 407 bp DNA fragment containing the metC promoter. This binding was stimulated by O-acetyl-L-serine. Competition experiments with deletion variants of the metC promoter showed that CmbR binding only occurred with fragments containing an intact DR2, confirming that DR2 is the CmbR binding site within the metC promoter.

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Regulation of the Salmonella typhimurium metA gene by the metR protein and homocysteine

Cited by 43 publications

References 28 publications

In vivo hydrolysis of S-adenosylmethionine induces the met regulon of Escherichia coli

In vivo hydrolysis of S-adenosylmethionine induces the met regulon of Escherichia coli

Homoserine O-acetyltransferase, involved in the Leptospira meyeri methionine biosynthetic pathway, is not feedback inhibited

Molecular characterization of the CmbR activator-binding site in the metC–cysK promoter region in Lactococcus lactis

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