BIOL 1000 Chapter Notes - Chapter 7: Gs Alpha Subunit, Heterotrimeric G Protein, Guanosine Diphosphate
Document Summary
The g protein-coupled receptor is activated by an external signal in the form of a ligand or other signal mediator. This creates a conformational change in the receptor, causing activation of a protein. The inactive g protein is bound to the receptor in its inactive state. Once the ligand is recognized, the receptor shifts conformation and, thus, mechanically activates the g protein, which detaches from the receptor. The receptor can now either activate another g protein or switch back to its inactive state. These g-proteins are a trimer of , , and subunits (known as g , g , and g , respectively) that is rendered inactive when reversibly bound to. Guanosine diphosphate (gdp) (or alternatively, no guanine nucleotide) but active when bound to guanosine triphosphate (gtp). Upon receptor activation, the gef domain, in turn, allosterically activates the g-protein by facilitating the exchange of a molecule of gdp for gtp at the g-protein"s -subunit. camp pathway.
