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In genetics, an operator is a segment of DNA to which a transcription factor binds to regulate gene expression. The transcription factor is a repressor, which can bind to the operator to prevent transcription. The main operator (O2) in the classically defined ''lac'' operon is located slightly downstream of the promoter. Two additional operators, O1 and O3 are located at -82 and +412, respectively. == Mechanism == The repressor protein physically obstructs the RNA polymerase from transcribing the genes. An inducer (small molecule) can displace a repressor (protein) from the operator site (DNA), resulting in an uninhibited operon. Alternatively, a corepressor can bind to the repressor to allow its binding to the operator site. A good example of this type of regulation is seen for the trp operon. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Operator (biology)」の詳細全文を読む スポンサード リンク
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