title: Effect of tryptic digestion of myosin subfragment-1 on its binding to F-actin.
abstract: We investigated the effect of tryptic digestion of S-1 (95K) into three segments (27K, 50K, and 20K) on the binding of F-actin with S-1, using an ultracentrifugal separation method and a light-scattering method. The tryptic digestion of S-1 decreased the affinity of S-1 for F-actin both in the absence of nucleotide and the presence of AMPPNP or ATP, suggesting that the peptide cutting impairs the structures participating in the binding of S-1 or S-1-nucleotide complex with F-actin. Although nucleotides markedly weakened the affinity of S-1 for F-actin, the ratios of affinity of digested S-1 for F-actin to that of intact S-1 were all about 1/10 both in the absence and presence of nucleotides. This may be understood if we accept the assumption that two kinds of structure participate in the binding of S-1 with F-actin; one is independent of nucleotides and the other is dependent on them, with only the former being affected by the tryptic digestion of S-1.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D007700:Kinetics; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism*; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D014357:Trypsin / Q000378:metabolism*
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D010446:Peptide Fragments; D000266:Adenylyl Imidodiphosphate; D014357:Trypsin; D009218:Myosins