General properties of ion channels Flashcards
What is the permeability of a membrane for ions a result of?
it is a result of the opening of discrete pores (ion channels)
How can the function of these discrete pores (ion channels) be studied?
patch clamp
What is the open probability equation?
What determines the probability of transitions among and opened and closed conformations of ion channel proteins?
rate constants
How does voltage and ligands affect gating?
changing the rate constants
the open probability is a function of this
What can gating schemes describe?
the kinetics of both individual and ion channels aswell as whole-cell ionic currents
Ion channel throughput rate approach the __________ (at physiological ion concentrations) ; while affording perfect selection among different types of ions.
diffusion limit
Ion channel conductance saturates at ____ ionic concentrations.
high
What do binding sites for ions in the pore explain?
- Δε ↓ = throughput rate ↑
- saturation at high ionic concentrations
- negatively charged Cl- ion excluded (cation selectively)
Describe the selectivity of ion channels.
Ion channels select even among identically charged ions
The pore contains _________ for the permeant ions.
permeant ions
- lower energy barrier, saturable conductance
Some ion channel pores simultaneously accommodate more than ___ ion
one
“signal file”
What determines selectivity of K+ and voltage-gated Na+ and Ca2+ channels?
conserved “p-loop” sequence
What is the structure of the K+ channel?
4-fold rotational symmetry
“inverted teepee” architecture
What is the mechanism of K+ permeation in light of the structure?
in the selectivity filter K+ ion are found in four positions, arranged in a single file
