Presentation on theme: "G-Protein-Linked Receptors What the Hell? By: Keven, Sam, and Cory."— Presentation transcript:
G-Protein-Linked Receptors What the Hell? By: Keven, Sam, and Cory
Basics: Called “g-protein linked receptors” because they BIND to the Guanine nucleotides: GDP and GTP. They are made of three different units (Alpha, Beta, and Gamma) that attach to: – The inner surface of the plasma membrane – “Transmembrane” receptors (G protein- coupled receptors, GPCRs for short).
How Do They Work? A wannabe, smart biologist asks.. In the inactive state, Gα (g- protein) has GDP in its binding site When a hormone or other “ligand” binds to GPCR, an allosteric change takes place in the receptor After the bind, the G-protein separates into Ga and GβGγ subunits GTP activates Gα causing it to dissociate from GβGγ- which remains as two subunits. Activated Gα activates an adenylyl cyclase, an enzyme in the inner plasma membrane, which catalyzes the conversion of ATP into cAMP. Activated Gα is now a GTPase so it quickly converts its GTP back to GDP. This conversion, tied with the return of the Gβ and Gγ subunits, restores the G protein to its inactive state
Cholera Well…What the Hell is it? Cholera is an infection in the small intestine caused by the bacterium Vibrio Cholerae. What happens on the cellular level? The Cholera toxin, an enzyme, transfers ADP from NAD + (an enzyme that transfers hydrogen) and adds it to a chain in the Gsa protein. This prevents the GTP from hydrolysis, so that the Gsa chain is left permanently in the stimulatory state. In essence, the cholera toxin enters the body through intestinal cells, it exerts a volume of fluid which expels and becomes far more than the intestinal system can handle. THUS, causing a large amount of watery diarrhea. WHEW OUTTA BREATH
Epinepherine Well…What the Hell is it (part II)? Epinephrine Animation