The protein whose removal enables myosin to bind actin in smooth muscle is

Options

(a) tropomyosin
(b) caldesmon
(c) myosin light chain kinase
(d) calmodulin

Correct Answer:

calmodulin

Explanation:

The protein caldesmon, originally isolated from smooth muscle tissue where it is the most abundant calmodulin-binding protein, has since been shown to have a wide distribution in actin- and myosin- containing cells where it is localized in sub-cellular structures concerned with motility, shape changes and exo- or endo-cytosis. Caldesmon is believed to be an actin- regulatory protein, and binds with high affinity to actin or actin-tropomyosin. Caldesmon inhibits the activation by actin-tropomyosin of myosin