repressor

biochemistry

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July 13, 2026

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In biochemistry, a repressor is a protein molecule that controls gene expression by preventing the synthesis of enzymes. This mechanism is most studied in microorganisms but is believed to occur in higher organisms as well.1

Repressors function within genetic regulatory systems like operons, which are found in bacteria and their viruses. In an operon, genes for related proteins are grouped on DNA. A repressor protein binds to an operator region of the DNA, blocking the action of RNA polymerase and thus preventing transcription. This process allows cells to conserve energy by producing proteins only when needed. For example, the lac operon in E. coli uses a lac repressor to turn off the production of lactose-metabolizing enzymes when lactose is absent.234

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gene
Gene regulation
…small protein molecule called a repressor. The repressor binds to the operator gene and prevents it from initiating the synthesis of the protein called for by the operon. The presence or absence of certain repressor molecules determines whether the operon is off or on. As mentioned, this model applies to…
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…small protein molecule called a repressor. The repressor binds to the operator gene and prevents it from initiating the synthesis of the protein called for by the operon. The presence or absence of certain repressor molecules determines whether the operon is off or on. As mentioned, this model applies to…
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induction
…specify a protein, called a repressor protein, that binds to the region of deoxyribonucleic acid (DNA) responsible for directing the synthesis of the enzyme. If substrate is present, it acts as an inducer by combining with the repressor so as to prevent its binding to DNA. As a result, the…
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…specify a protein, called a repressor protein, that binds to the region of deoxyribonucleic acid (DNA) responsible for directing the synthesis of the enzyme. If substrate is present, it acts as an inducer by combining with the repressor so as to prevent its binding to DNA. As a result, the…
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nucleic acid
Transcription
…“operators” where specialized proteins called repressors bind to the DNA just upstream of the start point of transcription and prevent access to the DNA by RNA polymerase. These repressor proteins thus prevent transcription of the gene by physically blocking the action of the RNA polymerase. Typically, repressors are released from…
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…“operators” where specialized proteins called repressors bind to the DNA just upstream of the start point of transcription and prevent access to the DNA by RNA polymerase. These repressor proteins thus prevent transcription of the gene by physically blocking the action of the RNA polymerase. Typically, repressors are released from…
Read More