Question

Protein kinase A activation typically involves

A. Binding of calcium ions to the 2 regulatory domains
B. Binding of cAMP to the inactive catalytic subunit
C. Phosphorylation of the kinase a domain
D. Binding of cAMP to the regulatory subunits
E. Phosphorylation of the regulatory subunits

Answer 1

The correct answer is option d. PKA is activated when cAMP binds to its regulatory subunits, causing a conformational change that releases active PKA catalytic subunits which then catalyze phosphorylation processes in the cell.

Step-by-step explanation:

Protein Kinase A Activation Mechanism

The activation of Protein Kinase A (PKA) involves a series of molecular interactions and conformational changes within the cell. When extracellular signals such as hormones bind to receptors on the cell surface, there is a propagation of the signal which eventually leads to the activation of a membrane-bound enzyme called adenylate cyclase. This enzyme synthesizes cyclic AMP (cAMP) from ATP, and it's the cAMP that binds to the regulatory subunits of PKA.

This binding leads to a conformational change that dissociates the inactive PKA tetramer into its active and inactive parts: two inactive cAMP-bound regulatory subunits and two active catalytic subunits. The active PKA enzymes can then catalyze phosphorylation reactions that activate other enzymes, like phosphorylase kinase, leading to various downstream cellular effects.