Actin and Myosin are contractile proteins while Troponin and Tropomyosin are regulatory proteins involved in muscle contraction. Myosin is important protein of Dark bands while remaining three are proteins of light bands. Actin consists of two F actins which is made up of many monomeric units G actin. Troponin masks the actin filament and thus covers the myosin binding sites. Tropomyosin are trimeric structures that run close to F actin.