9 - Regulated Proteolysis

Question 1

Give an example of regulated proteolysis

Answer 1

Ubiquitylation switch

Question 2

What is the ubiquitylation switch

Answer 2

• in principle the switch resembles the phosphorylation switch
• in an ATP-consuming reaction, the ubiquitin transferase complex transfers ubiquitin (UB) to a Lys residue of a substrate protein (see Figure 2.32) where it may be removed again by a deubiquitinase
• both ubiquitylation and de-ubiquitylation are controlled by input signals
• the conformational and functional change induced by ubiquitylation in the substrate protein is the output signal. - the switching energy is delivered by the hydrolysis of ATP or, to be precise, of pyrophosphate (PPi). This scheme applies to ubiquitin-like modifiers as well.