A closer view of the conformation of the Lac repressor bound to operator.
Crystal structures of the Lac repressor, with and without isopropyithiogalactoside (IPTG), and the repressor bound to operator have provided a model for how the binding of the inducer reduces the affinity of the repressor for the operator. However, because of the low resolution of the operator-bound structure (4.8 A), the model for the allosteric transition was presented in terms of structural elements rather than in terms of side chain interactions. Here we have constructed a dimeric Lac repressor and determined its structure at 2.6 A resolution in complex with a symmetric operator and the anti-inducer orthonitrophenylfucoside (ONPF). The structure enables the induced (IPTG-bound) and repressed (operator-bound) conformations of the repressor to be compared in atomic detail. An extensive network of interactions between the DNA-binding and core domains of the repressor suggests a possible mechanism for the allosteric transition.
Bell
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The Johnson Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, 37th and Hamilton walk, Philadelphia, Pennsylvania 19102-6059, USA.
Lewis
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D000494:Allosteric Regulation; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins; D006027:Glycosides / Q000737:chemistry / Q000378:metabolism*; D006860:Hydrogen Bonding; D007544:Isopropyl Thiogalactoside / Q000737:chemistry / Q000378:metabolism; D056968:Lac Repressors; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009875:Operator Regions, Genetic / Q000235:genetics*; D011487:Protein Conformation; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D055672:Static Electricity; D013329:Structure-Activity Relationship
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D006027:Glycosides; D056968:Lac Repressors; C539064:LacI protein, E coli; D012097:Repressor Proteins; C047034:2-nitrophenyl-beta-fucoside; D007544:Isopropyl Thiogalactoside; D004247:DNA