Lecture 8 Flashcards
- independant of plasma membrane proteins
- ion channels
- downstream of G-protein-coupled receptors
can small hydrophobic molecules freely diffuse across the membrane? where do they usually bind in the cell?
yes
nuclear receptor superfamily proteins
nuclear receptor superfamily protein structure
N-terminal transcription activating domain
middle: DNA binding domain
C-terminal: ligand binding domain
both the receptor and effector
are all nuclear receptor proteins localized to nucleus
no, some stay in cytoplasm until binding to signal molecule then move to nucleus
does nitric oxide interact with the nuclear receptor superfamilies
no, acts in smooth muscle cells of blood vessels to relax them
can only dissuse short distance
is light a ligand
no but it’s a signal
synaptic signaling uses what type of receptor
extracellular ligand gated ion channels, ligand binding opens channel
GPCR structure
7 TM domains and extracelular signal receptor that becomes active upon binding to act as GEF: exchanges GDP for GTP in G protein
G protein structure
heterotrimeric large G-protein complex: alpha, beta and gamma
alpha subunit has GDP, exchanged for GTP by active GPCR
active GTP bound G-alpha dissociates from beta and gamma
when beta and gamma separate from alpha, they also become an active dimer!
how to turn off GPCR-G protein signaling
G-alpha is actually a GTPase so over time will hydrolyze GTP to GDP
regulator of G protein signaling (RGS): very slow on it’s own though so GAP protein increases rate of GTP hydrolysis to GDP
are there different kinds of G proteins
yes! also don’t all rely on just alpha
how is cAMP made and turned off
adenylyl cyclase makes cAMP using ATP
phosphodiester enzymes break down cAMP to AMP to turn signaling pathway off
does cAMP activate or inactivate PKA? how?
activate
inactive PKA has 4 subunits: 2 regulatory and 2 catalytic (kinases)
2 cAMP bind to 2 regulatory subunits, releasing kinases so active
where does PKA go?
nucleus to phosphorylate CREB protein ACTIVATING it to promote transcription of certain genes
also activates other proteins
CRE
cAMP-responsive element
