Class Notes (834,176)
Canada (508,397)
York University (35,141)
Biology (2,227)
BIOL 2021 (188)

Ch. 15 - Cell Communication - Part 2 A summary of the chapter and lecture notes on cell communication, part 2. Includes illustrations and graphics from the textbook.

9 Pages
Unlock Document

BIOL 2021
Julie Clark

BIOL 2021- April 15 2009 CHAPTER 15 – PART 2: CELL COMMUNICATION G PROTEIN COUPLED RECEPTORS (GPCR) - Largest family - On surface - Take signals from the outside and transfer them - 700 GPCR in human genome - ½ of all drugs are targeted to these receptors/pathways - Always a multipass transmembrane protein with a 7 MEMBRANE SPAN (passes through the plasma membrane 7 times) Figure 1 G proteins - GPCR work through trimeric G-protein (3 subunits)  Alpha subunit binds GDP  Beta and gamma subunits form a complex  Alpha and gamma subunits are membrane bound and have fatty acids integral in plasma membrane  There are many G proteins that are specific for GPCR and target Figure 2 Monomeric G protein (1 subunit) - In trimeric proteins, GEF activated the exchange of GDP for GTP on GPCR (activating pathway) - Active receptor cause a conformational change of G protein to give an active G protein - Then GDP is exchanged for GTP (activated) - Many G proteins are activated by active receptors - Amplification-> small signal amplified to cause a big signal - Targets can be on ion channels or enzymes - Signal is ended by alpha GTPase which hydrolyses GTP-> GDP, making it inactive - TO inactivate receptor, receptor gets phosphorylated (receptor kinase)  Then arrestin protein binds which prevents it from activating any more G proteins Αβγ inactive (GDP bound) Separates to: α (active) and βγ (active) Hydrolysis of GTP: GDP-αβγ (inactive- α reconnect with βγ) Targets: enzyme produced small intracellular mediators (second messengers) 2 PATHWAYS - Cyclic AMP (CAMP) produced - Found in all animal cells, prokaryotes but NOT PLANTS - - Made by adenylyl cyclase - Destroyed by CAMP phosphodiesterase (cleaves phosphodiester bonds) - G protein = G5 = stimulatory - Medically important, G5 activates adenylyl cyclase causing CAMP production Cholera toxin (inhibitor): inhibits GTPase (stops from signalling) activity of α subunit of G5  CAMP remains high instead of dropping as it should  Effect in intestinal epithelial cells  CAMP causes efflux of Cl and water goes into gut (causing diarrhea to death) CAMP targets - Main target is protein kinase A (pkA) - pkA has two regulatory subunits and 2 catalytic subunits  needs four CAMP bound to be active  this releases catalytic subunits (active) which phophorylate proteins  serine/threonine specific amino acids are phosporylated by the subunits - pkA activates different targets in specialized cells EFFECTS OF PKA ACTIVATION - can have rapid effects (seconds) i.e. Glycogen metabolism in muscles - to turn off: 1) CAMP PHOSPHODIESTERKINASE: destroys CAMP 2) Prote
More Less

Related notes for BIOL 2021

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.