BIOL 331 Lecture 31: Cell Signalling (Part 2)
Document Summary
Cell signalling part 2: g-protein coupled receptors and camp. The receptor always undergoes a conformational change during activation or deactivation. Signal amplification takes place at key steps in cascade. Gtp-binding proteins (g-proteins) and common switches to regulate signal. Going from active to inactive requires the hydrolysis of gtp to form gdp and an inorganic phosphate. To go from inactive to active, gdp is exchanged for gtp (no phosphorylation) Gpcr work together with heterotrimeric g- proteins to relay signals (on right) Heterotrimeric g-proteins have 3 different polypeptide subunits: alpha, beta, and gamma. Subunits will relay signals from the ligand receptors to the cytoplasm and/or the nucleus. Alpha and gamma subunits are linked to membrane by lipid groups. Step 1: ligand binds to receptor, altering conformation and increasing the receptor"s affinity for g-proteins. Step 2: g-protein alpha subunit releases gdp and is replaced by gtp (exchange)