What type of protein is activated by the binding of a hormone to a receptor?

The binding of a hormone to its specific receptor on the surface of a target cell typically leads to the activation of G proteins. These proteins act as molecular switches inside cells and are crucial for transducing signals from the receptor into various intracellular responses. When the hormone binds to its receptor, it causes a conformational change in the receptor that activates the associated G protein. This activated G protein then initiates a cascade of events, often involving the activation or inhibition of other proteins, enzymes, or channels within the cell.

While enzymes, channel proteins, and transport proteins play essential roles in cellular functions, they are generally not considered to be directly activated by hormone binding in the same way G proteins are. Enzymes may be regulated by other mechanisms, channel proteins create pathways for ions, and transport proteins facilitate movement of substances across membranes. However, the specific activation that occurs with G proteins is key in hormone signaling pathways, as they are integral to ensuring that the hormone's message is effectively communicated within the cell.