A protein kinase (CK2)CKB3 can interact with and phosphorylate CCA1, which is a multisubunit protein with serine/threonine kinase activity.

TLS Online TPP Program

#Id: 2448

#Unit 3. Fundamental Processes

Blocking the activities of gyrase and topoisomerase therefore result in major changes in DNA supercoiling, which in turn affects transcription and replication.

TLS Online TPP Program

#Id: 2449

#Unit 3. Fundamental Processes

In the absence of both activator and repressor, RNA polymerase occasionally binds the promoter spontaneously and initiates a low level (basal level) of transcription. 

TLS Online TPP Program

#Id: 2450

#Unit 3. Fundamental Processes

The lac operator overlaps the promoter, and so the repressor bound to the operator physically prevents RNA polymerase from binding to the promoter and thus initiating RNA synthesis.

TLS Online TPP Program

#Id: 2451

#Unit 3. Fundamental Processes

Allolactose binds to the Lac repressor and triggers a change in the shape (conformation) of that protein. 

TLS Online TPP Program

#Id: 2452

#Unit 3. Fundamental Processes

In the absence of allolactose, the repressor is present in a form that binds its site on DNA (and so keeps the lac genes switched off ). 

TLS Online TPP Program

#Id: 2453

#Unit 3. Fundamental Processes

Allolactose binds to a part of the Lac repressor distinct from its DNA-binding domain.