Ligand Gated Ion Channels Flashcards
How can multi-cellular organisms respond specifically to particular stimuli. (2)
Selective expression of certain receptors AND molecules involved in signal transduction
What type of protein are ion channels
Transmembrane Proteins
3 essential functions of ion channels- (Fluids, Nerve and muscles, muscle contraction and ..)
a) Transport ions across membranes- secretion and absorption
b) Regulate membrane potentials- Nerve and muscle cells
c) Ca2+ influx into the cytoplasm- Secretion and muscle contraction
Alpha helices
a right hand helix conformation
Beta sheets
Beta strands connected laterally by multiple backbone hydrogen cells- 2/3
Subunits
Single protein that forms with others= forms protein complex
Transmembrane domain (TM)
Protein that spans the width of the membrane from the extracellular to intracellular sides (usually helical)
P-loop or pore
Pocket where ion will bind
classification of ion channels
Gating mechanism- Voltage or ligand
Ion selectivity of the pore- physical size and aa lining pore
main structural features of ALL ion channels
- how many a-helices make up a TM
2 or more
In a simple K+ ion channel- which side of the gate is closed
Cytoplasmic gate
Voltage Gated ion channels
-Two main functions
-Na+ and K+ create Active potentials in excitable cells
-Ca2+ transported into cytoplasm where 2nd messenger elicits cellular response
What structurally is different between a ‘simple’ ion channel (3) and (for example) a voltage gated one
Additional helices S1 and S4 form separate ‘voltage sensing domain’ laterally
Large polypeptides- extend into cytoplasm
Plugging mechanism
‘Transient’ Receptor potential (TRP) channels
-How are they similar to Voltage gated channels
-How do they differ
(unfinished)
1) similar structures…
2) Evolved to recept other stimuli- chemicals and chemical (tastes and smell?)
When calcium binds to ‘calmodulin binding’ on the ligand gated channel what happens to the pore.
Pore closes
-simple channels have how many subunits
-how many subunits per Voltage gated, TRP and ligand gated
-3
-4
Helicies that cross the lipid bilayer-
in simple channels
voltage gated
TRP and ligand gated
. 2
. 6-24
. 6
Which of the 4 channel types (simple, voltage, TRP and Ligand) have plugging mechanisms? (2)
Voltage gated and TRP
What do extracellular ligand binding sites do?
(i think)? they can read neurotransmitters
3 different amounts of subunits for extracellular ligand + gates-
Nicotenic etc
5, 4, and 3
Nicotenic have 5
what do each neuronal nAChRs (nicotinic Acetylcholine receptors) display different levels of depending on alpha and beta subunits
Each have different affinity, depending on composition and location
Where and what does the a4b2 subunits have a high affinity for
Cortex and hippocampus
high affinity to agonists, nicotine and varenicline
what does the mutation in nAChR causing Autosomal Dominant Nocturnal Frontal Lobe Epilepsy entail? (what do the receptors do?)
Receptor the stimuli late, causing overloaded reaction to neurotransmitters
REMEMBERING
A4B2
A= agonists (nicotine etc)
B= brain
2= structures in the brain
A4B2= agonists, 2 structures in brain
High affinity 4 agonists in the brain/ cortex and hippocampus
