Signal Transduction pt. 2 Flashcards
What are some second messengers?
-cyclic AMP
-inositol triphosphate
-diacylglycerol
-calcium ions
-cyclic GMP
What stimulates glycogen breakdown?
Epinephrine
What is amplification?
when enzymes activate enzymes, the number of affected molecules increase geometrically in an enzyme cascade, this amplifies the signal
What is a G-protein?
-guanine nucleotide-binding proteins
-bind and hydrolyze GTP
-there are two classes; heterotrimeric G proteins or small GTPases
What is a heterotrimeric G protein?
-membrane bound
-transmit signals from G-protein coupled receptors
What is a small GTPases?
-cytoplasmic
-regulate cell growth, differentiation, apoptosis
-many cancers have mutations in small G-proteins
How are G-proteins turned on and off?
By GTP hydrolysis: molecular switches
on: GTP bound active
Off: GDP bound inactive
What are G-protein coupled receptors?
-large group of transmembrane receptors
-transmit diverse signals
-almost 1000 in the human genome
-approx half of drugs activate or inhibit GPCR
-transverse the membrane 7 times
-N-terminus outside
C-terminus inside
More on heterotrimeric G-proteins; structure
-three subunits (alpha, beta, and gamma subunit, beta and gamma function as one subunit)
-approx 20 known
-intertact with receptors, bind and hydrolyze GTP, activate or inhibit effectors
Explain activation of cAMP-dependent protein kinase (PKA) by cAMP.
protein kinase A has 2 catalytic subunits and 2 regulatory subunits. R2C2 complex is inactive (inhibited by R).
cAMP binds to R. Complex dissociates, C is active.
This is a common method for regulation in signaling.
What are cAMP regulated processes?
-glycogenolysis
-lipolysis
-steriodogenesis
-transcrption
-thyroxine release
What is Cholera and pertussis toxin?
Act by ADP-ribosylating G-proteins
Cholera toxin: Activates Gs
Pertussis toxin: inactivates G1
Both increase cyclic AMP concentrations
Review mechanism in notes
done
Review mechanism in notes
done
