Lecture 22 Signaling at the cell surface continued (chapter 15) G-proteins and G-protein coupled receptors Visual cascade and Receptor adaptation

G-protein coupled Receptors: Rhodopsin (visual pigment) out Retinal (ligand) in Natural ligand (retinal) is inside the cavity

Why vision is a kind of smell?

7-TM domain G-protein coupled receptors (short list) a, b adrenergic R Muscarinic AChR Dopamine R Histamine R Prostaglandin PGE1 R GABAB R Substance P R Opiate R ADH (vasopressin VR1) R Angiotensin R Bradykinin R Glucagon R Ca2+ R Olfactory receptors (?) Taste receptors Rhodopsin these ligands come from outside

Beta2 Adrenergic receptor

FRET experiments indicate that activation of G-proteins occurs within seconds

KACh channel is regulated by G beta-gamma Gbg

The intracellular (second) messengers Cyclases Phospholipase Ca2+