Question

17) Ca₂₊ -calmodulin stimulates phosphorylation of myosin by

A) Ca₂₊ -ATPase.
B) focal adhesion kinase.
C) myosin light chain kinase.
D) ryanodine receptor.
E) titin.

Answer 1

Ca²+-calmodulin stimulates phosphorylation of myosin by interacting with proteins that expose actin-binding sites.

Step-by-step explanation:

In skeletal and cardiac muscle, phosphorylation of myosin is stimulated by Ca²+ -calmodulin. This occurs after specific binding sites on the actin have been exposed in response to the interaction between calcium ions (Ca²+) and proteins (troponin and tropomyosin) that shield the actin-binding sites. Calcium ions are also required for the contraction of smooth muscle, where they activate enzymes, which in turn activate myosin heads.