Final answer:
The beta-2 adrenergic receptor is coupled to the Gs protein, which activates adenylate cyclase. This leads to increased cAMP levels in the cell, resulting in the activation of PKA and subsequent cellular responses.
Step-by-step explanation:
Beta-2 Adrenergic Receptor and Gs Protein
The beta-2 adrenergic receptor is a type of G-protein-coupled receptor that, when activated, is coupled to the Gs protein. This coupling to the Gs protein leads to activation of an enzyme called adenylate cyclase. The activation of adenylate cyclase results in an increased intracellular concentration of the second messenger cyclic AMP (cAMP). Subsequently, cAMP activates cAMP-dependent protein kinase (PKA), which mediates various intracellular responses following hormone binding, such as the regulatory phosphorylation of numerous enzymes.
Adrenergic receptors, including the beta-2 adrenergic receptor, specifically bind to catecholamines such as adrenaline (epinephrine) and noradrenaline (norepinephrine). Upon activation by these ligands, the beta-2 adrenergic receptor interacts with the Gs protein, leading to the exchange of guanosine diphosphate (GDP) for guanosine triphosphate (GTP) on the alpha subunit of the Gs protein. The activated Gs alpha subunit then interacts with and activates adenylate cyclase, increasing cAMP production and activating PKA.