What is the heavy meromyosin (HMM) component?

The striated appearance of myofibrils is due to the distribution pattern of two important proteins - Actin and Myosin. The light bands contain actin and the dark bands contain myosin.The light bands in a myofibril contain actin and is called I-band or Isotropic bandThe actin filaments are thinner as compared to the myosin filamentsEach actin (thin) filament is made of two "F" (filamentous) actins helically wound to each other.Each "F" actin is a polymer of monomeric "G" (Globular) actinsTwo filaments of another protein, tropomyosin also run close to the "F" actins throughout its length.In the resting state a subunit of troponin masks the active binding sites for myosin on the actin filaments.The thick filament in a myofibril is made up of many monomeric proteins called Meromyosins.The HMM component consists of the head and short arm of a meromyosin.