Imagine that two protein kinases, PK1 and PK2, act sequentially in a kinase casc
ID: 91415 • Letter: I
Question
Imagine that two protein kinases, PK1 and PK2, act sequentially in a kinase cascade. When either kinase is completely inactivated, cells do not respond to the normal extracellular signal. By contrast, cells containing a mutant form of PK1 that is permanently active respond even in the absence of an extracellular signal. Doubly mutant cells that contain inactivated PK2 and permanently active PK1 respond in the absence of a signal. A. In the normal kinase cascade, does PK1 activate PK2 or does PK2 activate PK1? B. What outcome would you have predicted for a doubly mutant cell line with an activating mutation in PK2 and an inactivating mutation in PK1?Explanation / Answer
19.
A.PK2 activates PK1. This is because even when there is deactivation of PK2 and activation of PK1,the cell responds with functioning of PK1.
B.In this case if PK1 deactivation is permanent despite of activation by PK2 and as PK1 acts later in the signalling process, the cell will not respond to the signal.