BIO 211 Lecture Notes - Lecture 5: Phosphatidylinositol 4,5-Bisphosphate, Gs Alpha Subunit, Adenylyl Cyclase
Document Summary
G-protein-coupled receptors (gpcrs)- cell-surface receptors that mediate responses to signals from external locations, as well as other cells: signal molecules vary in structure and function, gpcrs have similar structures. Trimeric gtp-binding protein (g proteins)- activated when an extracellular signal molecule bonds to gpcr; responsible for coupling the receptor to enzymes or ion channels in the membrane. Alpha---> gdp bound when unstimulated (g protein is inactive: gtp binds, g protein is released. Some g proteins regulate the production of cyclic amp. Activates gpcrs that are coupled to stimulatory g proteins (gs)- activated adenylyl cyclase when gs alpha subunit binds. Inhibitory g protein (gi)- reduce camp levels when activated to inhibit adenylyl cyclase. Synthesized from atp by adenyl cyclase enzyme: destroyed by cyclic amp phosphodiesterase. Cyclic-amp-dependent protein kinase (pka) mediates most of the effects of cyclic. Cyclic-amp-dependent protein kinase (pka)- phosphorylates series or threonines on target proteins to regulate their activity. Inactive state has two catalytic subunits and two regulatory ones.