Voltage-Dependent Channels- Lecture 17

Question 1

What is an inward rectifier?

Answer 1

K+ selective channels that are formed by tetramers of homologous subunits with a water-containing pore of variable diameter in the center inside which are acidic residues that are accessible from the intracellular side of the channel, allowing for blockage of the pore by large cations (Mg2+ or larger polyamines such as spermine) that can only be dislodged by inward (against the gradient) movements of K+ (which normally happens when membrane is hyperpolarized)

Question 2

What is a voltage-gated channel?

Answer 2

ion selective channels (normally K+, Na+, or Ca2+) that open upon membrane depolarization

Question 3

What is the difference between K+ and Ca2+/Na+ voltage-gated channels?

Answer 3

K+ channels have four subunits where as the Na+/Ca2+ have a single polypeptide with 24 transmembrane helices arranged into four domains with six helices each