What happen to lac repressor in E. coli when lactose is present?

The lac repressor is a protein that binds to the lac operator and prevents the transcription of the lac operon, which is responsible for the metabolism of lactose. When lactose is present, the lac repressor undergoes a conformational change that causes it to release from the lac operator. This allows the transcription of the lac operon and the production of the enzymes necessary for lactose metabolism.

Here is a more detailed explanation of what happens to the lac repressor in E. coli when lactose is present:

1. When lactose is absent, the lac repressor is bound to the lac operator and prevents the transcription of the lac operon.

2. When lactose is present, it binds to the lac repressor and causes a conformational change.

3. The conformational change causes the lac repressor to release from the lac operator and the lac operon can now be transcribed.

4. The transcription of the lac operon produces the enzymes necessary for lactose metabolism.

5. The enzymes produced by the lac operon convert lactose into glucose and galactose, which can then be used by the cell as an energy source.

The lac repressor is a classic example of a negative regulator of gene expression. Negative regulators bind to DNA and prevent the transcription of genes. When the ligand is present, the negative regulator is released from the DNA and the genes can be transcribed.