What characterizes the B2 adrenergic receptor?

The B2 adrenergic receptor is characterized as an integral membrane protein that contains seven alpha-helices. This structure is typical of G protein-coupled receptors (GPCRs). The seven transmembrane domains of alpha-helices allow the receptor to span the plasma membrane and play a crucial role in the receptor's ability to transmit signals from extracellular ligands—such as hormones like epinephrine—into the interior of the cell. This transmembrane arrangement is essential for the receptor's function in signal transduction.

The receptor activates a G protein upon ligand binding, leading to a cascade of intracellular events. This is a fundamental aspect of GPCR functionality, as they rely on G proteins to relay signals and elicit physiological responses. Thus, recognizing that the B2 adrenergic receptor has multiple membrane-spanning regions, particularly seven alpha-helices, is key to understanding its structure and function within the broader context of biochemistry and cell signaling.