Question 1 Caldesmon is a regulatory protein in smooth muscle that binds to trop!
Question: Question 1 Caldesmon is a regulatory protein in smooth muscle that binds to tropomyosin and actin in thin fi?
Question 1
Caldesmon is a regulatory protein in smooth muscle that binds to tropomyosin and actin in thin filaments. When caldesmon binds to thin filaments, it inhibits the myosin ATPase. This action of caldesmon is inhibited when caldesmon is phosphorylated by protein kinase C or when caldesmon binds Ca2+-calmodulin. Imagine that a hormone binding to its receptor on a smooth muscle cell activates the mechanisms shown in the slide entitled “DAG/IP3 System” in the Cell Communication lecture. What would be the likely effect of this hormone on contraction of the smooth muscle cell?
Answer
a. The hormone would inhibit contraction.
b. The hormone would stimulate contraction.
c. The effect of the hormone cannot be predicted because of its opposite effects on caldesmon and myosin light chain kinase.
d. Don't choose this one. It's not the answer.
Caldesmon is a regulatory protein in smooth muscle that binds to tropomyosin and actin in thin filaments. When caldesmon binds to thin filaments, it inhibits the myosin ATPase. This action of caldesmon is inhibited when caldesmon is phosphorylated by protein kinase C or when caldesmon binds Ca2+-calmodulin. Imagine that a hormone binding to its receptor on a smooth muscle cell activates the mechanisms shown in the slide entitled “DAG/IP3 System” in the Cell Communication lecture. What would be the likely effect of this hormone on contraction of the smooth muscle cell?
Answer
a. The hormone would inhibit contraction.
b. The hormone would stimulate contraction.
c. The effect of the hormone cannot be predicted because of its opposite effects on caldesmon and myosin light chain kinase.
d. Don't choose this one. It's not the answer.
Answers:
the answer is B
if you look at the slide he mentions, you see that when protein kinase C phosphorylates a protein it results in a cellular response. So since muscles use the myosin to contract, and caldesmon inhibits myosin ATPase, inhibiting the caldesmon thru phosphorylation will allow the signal transduction to function normally and the muscle will contract.