Interactions of the Escherichia coli methionine repressor with the metF operator and with its corepressor, S-adenosylmethionine.

Saint‐Girons, Isabelle; Belfaiza, J; Guillou, Yvonne; Perrin, Dominique; Guiso, Nicole; Bârzu, Octavian; Cohen, Georges N.

doi:10.1016/s0021-9258(18)67477-0

Cited by 58 publications

(16 citation statements)

References 33 publications

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“…To date, however, a detailed investigation of the binding energetics in the MetJ system has not been undertaken. Earlier studies focused on measuring binding affinities for substrates with multiple metboxes and have suffered from secondary binding events to nonoperator DNA and the formation of higher order complexes that bind more than one MetJ dimer per metbox (Saint-Girons et al, 1986, 1988Phillips et al, 1989; Kirby and Greene, personal communication). Recently, a communication has been published describing calorimetric results for selected pathways of the MetJ system (Cooper et al, 1994).…”

Section: Eachmentioning

confidence: 99%

“…These data clearly indicate that MetJ repressor dimer binds specifically to the central region of its 8 bp cognate metbox operator but recognizes partial operator sequences as short as 6 bp. Cooperativity in binding of operator sequences from which a palindromic consensus MetJ binding site has been culled (Belfazia et al, 1986;Saint-Girons et al, 1986). This sequence, 5'-AGACGTCT-3', is often referred to as a "metbox".…”

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confidence: 99%

“…This overall mechanism for repression of the biosynthetic path for methionine is illustrated schematically in Figure 1 (Cohen & Jacob, 1959; Saint-Girons et al, 1994, 1988; Old et al, 1991). There are a number of naturally occurring 0006-2960/95/0434-3212$09.00/0 A number of studies have been reported on the interactions of MetJ with both wild-type and consensus operator sequences, in which the proposed MetJ binding site is centered on the junction between metboxes (Saint-Girons et al, 1986;Davidson & Saint-Girons, 1989;Phillips et al, 1989). The X-ray structure of the protein-DNA cocrystal, however, shows binding in the center of each metbox (Somers & Phillips, 1992).…”

mentioning

confidence: 99%

“…The MetJ protein forms a homodimer of 12 kDa monomer units (Saint-Girons et al, 1986;Rafferty et al, 1989). Mediumto high-resolution crystal structures are available for the protein: without corepressor, apoMetJ; with SAM, holoMetJ (Rafferty et al, 1989); and bound to its DNA recognition sequence with SAM (Somers & Phillips, 1992).…”

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confidence: 99%

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Thermodynamic Evaluation of Binding Interactions in the Methionine Repressor System of Escherichia coli using Isothermal Titration Calorimetry

Hyre¹,

Spicer²

1995

Biochemistry

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The binding interactions of the methionine repressor protein, MetJ, from Escherichia coli with its cognate, metbox DNA sequence and corepressor S-adenosylmethionine were examined using calorimetric methods. A detailed thermodynamic characterization of this system which exhibits the recently reported (beta alpha alpha)2 binding motif provides values for delta G, delta H, and delta S for each step in the repressor binding cycle. These studies show that, in the presence of corepressor, MetJ binds to a single metbox operator site with delta G = -7.7 kcal.mol-1, whereas in the absence of corepressor, the free energy of interaction with a single site is -5.8 kcal.mol-1. Cooperative interactions between two repressor molecules bound to two adjacent sites contribute an additional free energy of -1.3 kcal.mol-1 to binding at the second site. Binding is enthalpically unfavorable in the absence of the corepressor with delta H = +2.6 kcal.mol-1 but becomes exothermic with delta H = -4.6 kcal.mol-1 when corepressor is present. The heat capacity for the system decreases significantly by delta Cp = -290 cal.mol-1.K-1 on a per site basis when the protein binds to DNA, and interactions between repressor molecules bound to adjacent sites contribute a delta Cp = -800 cal.mol-1.K-1, indicating that solvent exclusion plays a significant role in binding in this system. The corepressor binds to the unbound repressor protein with a free energy of delta G = -6.0 kcal.mol-1 and to the MetJ-operator complex with delta G = -6.95 kcal.mol-1. Repressor binding to random-sequence DNA was estimated to occur with a free energy of -5.7 kcal.mol-1 in the presence of corepressor. These data clearly indicate that MetJ repressor dimer binds specifically to the central region of its 8 bp cognate metbox operator but recognizes partial operator sequences as short as 6 bp. Cooperativity in binding of adjacent MetJ dimers to a double metbox sequence is demonstrated to be important in determining the energetics of the interaction. Finally, the corepressor S-adenosylmethionine enhances the affinity of MetJ for its recognition site DNA by a factor of 25 and contributes significantly to the net exothermicity of repressor binding.

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Section: Eachmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Thermodynamic Evaluation of Binding Interactions in the Methionine Repressor System of Escherichia coli using Isothermal Titration Calorimetry

Hyre¹,

Spicer²

1995

Biochemistry

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“…Studies of the regulation of methionine synthesis in bacteria, extensively reviewed by Saint-Girons et al (1988) and Old et a l . (1991), laid some of the early foundations for our understanding of regulation of gene expression.…”

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Structure and function of Escherichia coli met repressor: similarities and contrasts with trp repressor

Phillips

Stockley

1996

Phil. Trans. R. Soc. Lond. B

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Transcription of genes encoding enzymes for the biosynthesis of methionine and trytophan in Escherichia coli is regulated by the ligand-activated met and trp repressors. X-ray crystallographic studies show how these two small proteins, although similar in size and function, have totally different three-dimensional structures and specifically recognize their respective DNA operator sequences in different ways. A common feature is that both repressors bind as cooperative arrays to tandem repeats of 8 base-pair 'Met' or 'Trp boxes' respectively, and the consensus sequences share the rare tetranucleotide CTAG. A series of structural and functional studies have shown how the two repressors discriminate between their operators, using a combination of direct contacts between side chains and bases, and indirect sensing of conformational properties of the DNA.

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DNA, Repressor-Operator Recognition

Stockley

Phillips

2006

Encyclopedia of Molecular Cell Biology and Molecular Medicine

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Interactions of the Escherichia coli methionine repressor with the metF operator and with its corepressor, S-adenosylmethionine.

Cited by 58 publications

References 33 publications

Thermodynamic Evaluation of Binding Interactions in the Methionine Repressor System of Escherichia coli using Isothermal Titration Calorimetry

Thermodynamic Evaluation of Binding Interactions in the Methionine Repressor System of Escherichia coli using Isothermal Titration Calorimetry

Structure and function of Escherichia coli met repressor: similarities and contrasts with trp repressor

DNA, Repressor-Operator Recognition

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