Please choose the best option for each part and explain why it is correct: Part
ID: 3519084 • Letter: P
Question
Please choose the best option for each part and explain why it is correct:
Part 1: In the paper 'Distinct contributions of the thin and thick filaments to length-dependent activation in heart muscle measurement to show that length dependent activation of the thin-filament correlates with passive force on the myosin thick filament and not active ATPase cycling by myosin catalytic domains' by Zhang et. al (2017), the authors use what type of measurement to show that length dependent activation of the thin-filament correlates with passive force on the myosin thick-filament and not active ATPase cycling by myosin catalytic domains?
a. The calcium dependence of Myosin ATPase inhibition.
b. Sarcomere length dependent changes in the orientation of myosin’s regulatory light-chain in combination with ATPase inhibition by blebbistatin.
c. Sarcomere length dependent changes in the orientation of troponin C during active ATPase cycling.
d. Maximum skeletal muscle shortening velocity.
e. Fluorescence detection of cytosolic calcium.
Part 2: The Latch state most likely reflects the force and phosphorylation dependent accumulation of what biochemical species in the actomyosin ATPase cycle?
a. Myosin.ATP
b. Myosin.ADP .Pi
c. Actomyosin
d. Actomyosin.ADP
e. Myosin.ADP
Part 3: When smooth muscle myosin is dephosphorylated which of the following is true:
a. ATP binding is prevented
b. Actin-activated phosphate release is prevented
c. Actin-activated ADP release is accelerated
d. Actin binding is accelerated
e. Myosin monomers unfold
Part 4: (True/False) Phosphorylation of Myosin Binding Protein C by Protein Kinase A increases the probability that Myosin binding protein C will bind to Cardiac Myosin.
Explanation / Answer
Answer part 1. Option e
They used the fluorescence method to detect the amount of calcium in the thick and the thin filaments of the heart muscles.
Answer part 2. Option b
As per latch mechanism, the smooth muscles have high ATP requirement due to the phosphorylation of the myosin light chain. Thus when they will utilise ATP it will be hydrolysed to ADP and Pi, these both will bind to the myosin.
Answer part 3. Option e
Dephosphorylation leads to the termination of the muscle contraction because it brings structural changes in the myosin monomers by unfolding.
Answer part 4. True
Myosin binding protein C in humans is synthesized by the MYBPC3 gene.
It is required for normal functioning of the heart, any abnormality in it leads to cardiac hypertrophy.