Acetylcholine binds to a G-coupled protein receptor on the heart muscle to make
ID: 252192 • Letter: A
Question
Acetylcholine binds to a G-coupled protein receptor on the heart muscle to make the heart beat more slowly. It does so by stimulating the opening of K+ channels in the plasma membrane, which makes it more difficult to initiate and action potential. Describe the following on contraction of the heart.
A.) Addition of a drug that inhibits the GTPase activity of the Ga subunit.
B.) Mutations in the K+ channel that keep it closed all the tiem.
C.) A mutation that decreases the affinity of the (Beta gamma) complex of the G protein for the K+ channel.
Explanation / Answer
A) Addition of a drug that inhibits the GTPase activity of the Ga subunit:
This condition decreases the affects of acetylcholine, so increases the heart rate.
B) Mutations in the K+ channel that keep it closed all the time:
This condition also decreases the affects of acetylcholine, so it increases the heart rate.
C) A mutation that decreases the affinity of the (Beta gamma) complex of the G protein for the K+ channel:
This condition also decreases the affects of acetylcholine, so that it increases the heart rate.