Structural basis of gene regulation by the tetracycline inducible Tet repressor-operator system.
The tetracycline repressor (TetR) regulates the most abundant resistance mechanism against the antibiotic tetracycline in grain-negative bacteria. The TetR protein and its mutants are commonly used as control elements to regulate gene expression in higher eukaryotes. We present the crystal structure of the TetR homodimer in complex with its palindromic DNA operator at 2.5 A resolution. Comparison to the structure of TetR in complex with the inducer tetracycline-Mg2+ allows the mechanism of induction to be deduced. Inducer binding in the repressor core initiates conformational changes starting with C-terminal unwinding and shifting of the short helix a6 in each monomer. This forces a pendulum-like motion of helix a4, which increases the separation of the attached DNA binding domains by 3 A, abolishing the affinity of TetR for its operator DNA.
Orth
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Institut für Chemie, Kristallographie, Freie Universität Berlin, Takustr. 6, D-14195 Berlin, Germany.
Schnappinger
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Hillen
W
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Saenger
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Hinrichs
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D000494:Allosteric Regulation / Q000187:drug effects; D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009875:Operator Regions, Genetic / Q000235:genetics*; D011487:Protein Conformation / Q000187:drug effects; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017385:Sequence Homology; D015398:Signal Transduction / Q000187:drug effects; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013752:Tetracycline / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; D012097:Repressor Proteins; C034811:tetracycline resistance-encoding transposon repressor protein; D013752:Tetracycline; D008274:Magnesium