Q.ATPase enzyme needed for muscle contraction is located in:

Muscle contraction depends on two contractile proteins and two regulatory proteins organised into the sarcomere's filaments.

Thick filaments are bundles of myosin molecules. Each myosin molecule has a globular head (bearing an actin-binding site, an ATP-binding site, and ATPase activity) attached via a flexible hinge to a long tail; the head-bearing short arm is the heavy meromyosin (HMM) and the tail is the light meromyosin (LMM). Myosin molecules bundle together with heads projecting from opposite ends of the filament. …