In cell biology, PKA, or protein kinase A, is a crucial enzyme family. It's a serine/threonine kinase, meaning it adds phosphate groups to serine and threonine amino acids within other proteins. This phosphorylation changes the target protein's activity, impacting various cellular processes.
PKA's Role as a Master Regulator
PKA is widely known as a master regulator because its activity controls many cellular functions. It's activated by cyclic AMP (cAMP), a molecule acting as a cellular messenger responding to various stimuli. Higher cAMP levels lead to increased PKA activity.
- Ubiquitous Expression: Found in most mammalian cells.
- Diverse Activation: Triggered by a wide range of biological signals.
- Extensive Substrate Range: Phosphorylates over 250 known proteins.
The impact of PKA is far-reaching, influencing:
- Metabolism: Regulating energy production and utilization within cells.
- Growth and Development: Affecting cell division and differentiation.
- Neuronal Function: Playing a role in synaptic plasticity and memory formation. [See reference: The molecular biology of memory: cAMP, PKA, CRE, CREB-1 ...]
- Immune Responses: Modulating the activity of immune cells, like T cells. [See reference: A most versatile kinase: The catalytic subunit of PKA in T-cell biology]
- Signal Transduction: Participating in many signal cascades involving G protein-coupled receptors (GPCRs). [See reference: Smoothened transduces Hedgehog signals via activity-dependent ...]
PKA Structure and Function
PKA exists as a tetramer – a complex of four subunits. Two regulatory (R) subunits bind cAMP, and two catalytic (C) subunits perform the phosphorylation. cAMP binding causes a conformational change, releasing the catalytic subunits to phosphorylate target proteins.
[Note: The provided references mention pKa in the context of acid strength, which is a different concept from Protein Kinase A. This answer focuses solely on PKA in the biological context.]
