actomyosin: a protein complex in muscle fibers; composed of myosin and actin; shortens when stimulated and causes muscle contractions
protein: any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes
amino: the radical -NH2