- DNA-binding repressors – block the binding of RNA polymerase to the promoter. As a result, the gene is prevented from being transcribed into mRNA
- RNA-binding repressors – bind to mRNA, preventing protein translation
Examples of repressor proteins are lac repressor that inhibits the expression of lac operon in E. coli. Another is MetJ, a methionine repressor of met operon.
Repressor proteins are influenced by the presence of other molecules, such as corepressors and inducers. Corepressors are molecules that bind and activate repressors. Inducers, on the other hand, bind and regulate repressors by inducing the latter to undergo conformational change thereby decreasing binding affinity to the operator.
- lac operon
- promoter gene
- regulator gene