F-Protein, a myofibrillar protein interacting with myosin

F-Protein has an amino acid composition distinctively different from those of myofibriller proteins so far reported to be of similar chain weight: M-protein component II, alpha-actinin, and AMP deaminase. Its molecular weight was estimated to be 121,000 by sedimentation equilibrium in 0.3 M KCl, 10 mM potassium phosphate, pH 6.5. Its binding to myosin was inhibited by C-protein. It reduced the effect of C-protein on the assembly reaction of myosin in vitro.