Meromyosin

In Human anatomy, Myosin, of which meromyosin is a part of, along with actin constitute the basic functional unit of a muscle fibre, called Sarcomere. A better understanding of this subject can be reached once Muscle contraction is understood.

In biochemistry, meromyosin (mero meaning "part of") are subunits of the actin-associated motor protein, myosin, formed by trypsin digestion (proteolysis). Following digestion, two types of meromyosin are formed: heavy meromyosin (HMM) and light meromyosin (LMM).

Light meromyosin has a long, straight portion in the “tail” region. Heavy meromyosin is a protein chain terminating in a globular head portion/cross bridge. HMM consists of two subunits, Heavy Meromyosin Subunit 1 and 2 (HMMS-1 and HMMS-2). The majority of myosin activity is concentrated in HMMS-1. HMMS-1 has an Actin binding site and ATP binding site (myosin ATPase) that determines the rate of muscle contraction when muscle is stretched.

Light and Heavy meromyosin are subunits of Myosin filaments (thick myofilaments).