What is the role of the activated α-subunit in Step 3 of epinephrine signal transduction?

The activated α-subunit plays a critical role in epinephrine signal transduction as it separates from the βγ-complex and activates adenylyl cyclase, an enzyme crucial for the signaling cascade. When epinephrine binds to its receptor, it leads to the activation of a G-protein, which consists of three subunits: α, β, and γ. The binding of epinephrine causes a conformational change in the receptor, facilitating the exchange of GDP for GTP on the α-subunit. Upon activation, the α-subunit dissociates from the βγ-complex.

The activation of adenylyl cyclase by the α-subunit results in the conversion of ATP to cyclic AMP (cAMP), a second messenger that amplifies the signal within the cell and leads to various physiological responses, such as the mobilization of energy reserves. This process is pivotal for translating the hormonal signal into a biological response.

Other options do not accurately describe the function of the activated α-subunit in this context. For instance, the movement to protein kinase A involves cAMP as a secondary messenger rather than being a direct action of the α-subunit. DNA transcription is typically associated with nuclear signaling events, not the immediate actions