title: Kinetics of conformational change of troponin-C induced by binding or removal of calcium ion.
abstract: The kinetics of conformational change of troponin-C (TN-C) induced by binding or removal of calcium ion were studied in the presence or absence of magnesium ion by measuring the fluorescence of tyrosyl residues by stopped-flow spectrofluorometry. The result was analyzed in terms of first-order kinetics. Two phases were observed both in pCa-up and in pCa-down experiments. The dependence of the rate constants on pCa was explained by a simple mechanism as follows; (see article). The dissociation constants of calcium bound to TN-C, K and K', calculated from the experimentally determined rate constants were K = 3.16 X 10(-7) M, K' = 1.58 X 10(-6) M in the absence of magnesium ion, and K = K' = 1 X 10(-6) M in the presence of 2 mM MgCl2.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002942:Circular Dichroism; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008301:Maleimides; D009124:Muscle Proteins / Q000378:metabolism; D009281:Naphthalenes; D011487:Protein Conformation; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D014336:Troponin / Q000378:metabolism; D014443:Tyrosine
chemical_list: D008301:Maleimides; D009124:Muscle Proteins; D009281:Naphthalenes; D014336:Troponin; D014443:Tyrosine; D008274:Magnesium; D002118:Calcium