Trimeric G-proteins

Trimeric G-proteins are transducers which convert a signal from the G-protein linked receptor onto other proteins on the plasma membrane. The trimeric G-protein consists of 3 heterologous subunits named alpha, beta and gamma. The alpha subunit is a GTP-ase which binds GDP in its resting state. When the G-protein is activated by an external signal it splits into the activated alpha subunit (which is now bound to GTP) and the activated beta-gamma complex. Depending on the signalling pathway, either one of these molecules can be the one to interact with the enzyme in the next step of the cell signalling process.