Advanced Molecular Genetics-Biology 566 Prokaryotic - Polymerase Activation, Promoter Activation, Silencing
	Index CourseInfo LogIn Syllabus References Other Resources

Polymerase Activation

Figure 1.19. Sigma54 -containing polymerase and activation by NtrC. In the absence of nitrogen, NtrB phosphorylates NtrC which then works as an activator of the RNA polymerase, converting it from a stable closed complex to an active open complex. (A) Nitrogen present. (B) No nitrogen, NtrC activated. (C) Very high concentrations of NtrC can activate RNA Polymerase.

Question: How can you distinguish between a positive activator and polymerase activation?

Promoter Activation

Figure 1.20. Activation by MerR. The promoter bears the -10 and -35 elements on nearly opposite sides of the helix. In the absence of mercury, MerR binds with polymerase to form an inactive complex (top line). In the presence of mercury, MerR twists the DNA so as to properly align the promoter elements (bottom line).