Studies of the interaction of troponin I with proteins of the I-filament and calmodulin.
1. All lysine residues in native troponin I from rabbit fast-twitch skeletal muscle reacted with methyl acetimidate and ethyl acetimidate. 2. The reactivity of lysine-18 of troponin I to acetimidate was much diminished when the troponin I was complexed in the presence of Ca2+ with troponin C alone or in the whole troponin complex. 3. In the presence of EGTA, lysine-18 of troponin I in the troponin I-troponin C complex was more reactive to acetimidate than it was in the presence of Ca2+. 4. No masking of lysine residues could be detected when troponin I interacted with calmodulin or actin. 5. Sedimentation-equilibrium studies indicated that the complex of troponin I with calmodulin was more readily dissociated in the absence of Ca2+ than was its complex with troponin C under otherwise identical conditions. 6. These studies suggest that the nature of the involvement of the N-terminal region of troponin I is a major difference between its modes of interaction with calmodulin and with troponin C.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002850:Chromatography, Gel; D007096:Imidoesters / Q000378:metabolism; D046911:Macromolecular Substances; D008970:Molecular Weight; D009124:Muscle Proteins / Q000378:metabolism*; D010446:Peptide Fragments / Q000302:isolation & purification; D011817:Rabbits; D014336:Troponin / Q000378:metabolism*; D019209:Troponin C; D019210:Troponin I
D000596:Amino Acids; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D007096:Imidoesters; D046911:Macromolecular Substances; D009124:Muscle Proteins; D010446:Peptide Fragments; D014336:Troponin; D019209:Troponin C; D019210:Troponin I; D002122:Calcium Chloride