Abstract
Gal repressosome assembly and repression of the gal operon in Escherichia coli occurs when two dimeric GalR proteins and the histone-like HU protein bind to cognate sites causing DNA looping. Structure-based genetic analysis defined the GalR surfaces interacting to form a stacked, V-shaped, tetrameric structure. Stereochemical models of the four possible DNA loops compatible with the GalR tetramer configuration were constructed using the sequence-dependent structural parameters of the interoperator DNA and conformation changes caused by GalR and asymmetric HU binding. Evaluation of their DNA elastic energies gave unambiguous preference to a loop structure in which the two gal operators adopt an antiparallel orientation causing undertwisting of DNA.
MeSH terms
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Amino Acid Substitution / genetics
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Bacterial Proteins / metabolism
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Binding Sites
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DNA, Bacterial / chemistry*
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DNA, Bacterial / genetics
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DNA, Bacterial / metabolism*
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DNA-Binding Proteins / metabolism
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Dimerization
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Elasticity
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Escherichia coli Proteins
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Escherichia coli* / chemistry
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Escherichia coli* / genetics
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Kinetics
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Models, Molecular
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Mutation / genetics
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Nucleic Acid Conformation*
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Operon / genetics
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Protein Structure, Quaternary
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Repressor Proteins / chemistry
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Repressor Proteins / genetics*
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Repressor Proteins / metabolism*
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Structure-Activity Relationship
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Thermodynamics
Substances
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Bacterial Proteins
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DNA, Bacterial
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DNA-Binding Proteins
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Escherichia coli Proteins
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Galactose repressor proteins
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Repressor Proteins
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histone-like protein HU, bacteria