title: Changes of lysine reactivities of actin in complex with myosin subfragment-1, tropomyosin and troponin.
abstract: The interactions of actin with myosin subfragment-1 and tropomyosin were explored by comparing the reactivities of lysine residues in F-actin alone with those in F-actin complexed to the other proteins. Limited reductive methylation was carried out on F-actin and the F-actin complexes with [14C]HCHO and [3H]HCHO, respectively. After dissociation from the other components, [3H]actin was combined with [14C]actin and 3H/14C of each lysine residue was measured. Myosin subfragment-1 reduced the reactivities of Lys-335 and Lys-372, while tropomyosin reduced those of Lys-237, -325, 327 and -335. When troponin was present in the absence of Ca2+, the effect of tropomyosin on Lys-335 remained the same, but its reactivity was completely restored upon the addition of Ca2+. Thus, the results suggest that different parts of actin are affected by the interaction with myosin subfragment-1 and tropomyosin, but the region containing Lys-335 is commonly affected by the presence of either of them. The change in reactivity is attributable either to a direct steric effect or to an induced conformational effect.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002122:Calcium Chloride / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D008239:Lysine; D046911:Macromolecular Substances; D009124:Muscle Proteins / Q000378:metabolism*; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011485:Protein Binding; D014335:Tropomyosin / Q000378:metabolism*; D014336:Troponin / Q000378:metabolism*
chemical_list: D000199:Actins; D046911:Macromolecular Substances; D009124:Muscle Proteins; D015879:Myosin Subfragments; D010446:Peptide Fragments; D014335:Tropomyosin; D014336:Troponin; D004533:Egtazic Acid; D009218:Myosins; D008239:Lysine; D002122:Calcium Chloride