Lac repressor

What is the lac repressor?What is the lac repressor?

Repressors are proteins that inhibit the expression of genes; that is, they inhibit the transcription of messenger RNA from their target genes. Each repressor targets a specific co-regulated group of genes by recognizing a specific sequence of DNA, called the operator in bacteria. Repressor proteins are coded for by regulatory genes.

The lac repressor controls the expression of bacterial enzymes involved in the metabolism of of the sugar lactose. It, and the group of genes it controls, called an operon, were the first such gene regulatory system to be discovered.

For a general introduction to the lac repressor, please see David Goodsell's Introduction to the lac repressor in his series Molecule of the Month, and the article in Wikipedia on the lac repressor.