title: Gal repressosome contains an antiparallel DNA loop.
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.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: M
authors.initials: M
authors.lastname: Geanacopoulos
authors.forename: G
authors.initials: G
authors.lastname: Vasmatzis
authors.forename: V B
authors.initials: VB
authors.lastname: Zhurkin
authors.forename: S
authors.initials: S
authors.lastname: Adhya
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000378:metabolism; D001665:Binding Sites; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D019281:Dimerization; D004548:Elasticity; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D029968:Escherichia coli Proteins; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation; D009876:Operon / Q000235:genetics; D020836:Protein Structure, Quaternary; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C050993:Galactose repressor proteins; D012097:Repressor Proteins; C040330:histone-like protein HU, bacteria