title: Interaction between myosin and F-actin. Correlation with actin-binding sites on subfragment-1.
abstract: F-Actin bindings to subfragment-1 (S-1) and S-1 after limited proteolysis by trypsin (S-1t) were studied in the absence and presence of ATP by means of ultracentrifugation. No significant difference in the affinities for F-actin was observed between S-1 and S-1t in the absence of ATP. In contrast, the affinity for F-actin in the presence of ATP was decreased about 50 times by the limited proteolysis of the S-1 heavy chain. The S-1 whose SH1 and SH2 groups were cross-linked by N,N'-p-phenylenedimaleimide bound F-actin weakly. The affinity for F-actin was similar to that of unmodified S-1 in the presence of ATP and was also decreased markedly by limited proteolysis of the cross-linked S-1. Reciprocals of the dissociation constant of acto-S-1 complex decreased markedly with increase of ionic strength in the presence of ATP, but decreased only slightly at the rigor state. All these results are consistent with our proposal that S-1 has two different actin binding sites, as reported previously (Katoh, T., Imae, S., & Morita, F. (1984) J. Biochem. 95, 447-454). The mechanism of activation of S-1 ATPase by F-actin is discussed.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D009994:Osmolar Concentration; D010446:Peptide Fragments / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D009218:Myosins