G-proteins can either _______ or _______ an effector.

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G-proteins regulate signaling by acting as switches that modulate effector activity. When a G-protein is activated, it can turn an effector on or off, depending on the specific protein involved. For example, certain G-proteins (like Gs) activate adenylyl cyclase to raise cAMP levels, while others (like Gi) inhibit adenylyl cyclase to lower those levels. Similarly, Gq proteins activate phospholipase C, leading to different second-messenger cascades. The key idea is that the functional outcome on the effector is either activation or inhibition, not just binding, release, or phosphorylation. Phosphorylation is carried out by kinases, not by G-proteins themselves, and while G-proteins influence binding events, the defining action is changing the effector’s activity toward activation or inhibition.