MYOSIN
Myosin in eukaryotic cells constitutes 0.3 to 1.5% of total cell protein. Myosin interacts with actin and transforms the energy, which is released during hydrolysis of ATP, into the strength of a muscle contraction. A molecule of myosin consists of two identical chains of 2000 amino acids in each. In the tail region the double chain forms two projecting heads performing ATPase activity. Many isoforms of myosin with heavy and light chains have been extracted from muscle tissues of birds and mammalians.