A repressor is an RNA or DNA binding protein that prevents the expression of genes by attaching to the operator or related silencers.
A repressor protein binding to the DNA prevents the RNA polymerase from attaching to the promoter and transcribing the genes into mRNA or messenger RNA. The mRNA is bound by an RNA-binding repressor, which stops the mRNA from being translated into protein. Repression is the term for this suppression or reduction of expression.
Repressor proteins include lac repressor, which prevents the expression of the lac operon in E. coli. Another is the met operon’s methionine repressor MetJ.
Other compounds, such as corepressors and inducers, impact repressor proteins. Repressors can be bound to and activated by molecules called corepressors. On the other hand, inducers bind and control repressors by causing a conformational change and lowering bonding affinity to the operator.
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