Interaction Between Calmodulin and Target Proteins
When myosin light chain kinase (MLCK) activity was measured at various different free Ca2+ concentrations, the activity attained abruptively the maximum value within a very narrow concentration range of Ca2+. A result of this phenomenon is shown in Fig.1 (curve e), accompanied with the Ca2+ binding curve of calmodulin (curve a) (1). Since the Ca2+-calmodulin is known to work as an activator of MLCK, a large difference between the enzyme activation curve and the Ca2+ binding curve of calmodulin indicates that Ca2+ effect on the MLCK activity can not directly be explained by the comparison of these two curves. Olwin et al. have already shown that the affinity of Ca2+ to calmodulin was largely enhanced by the addition of MLCK (2). It is expected that the analysis of enhancing effect of MLCK to-the Ca2+ binding to calmodulin may give an answer how the enzyme attains the maximum activity within such a narrow concentration range of Ca2+ and how the Ca2+ concentration is fixed to this range. The Ca2+ binding to calmodulin was measured in the presence of mastoparan (curve c in Fig. 1) (3). Mastoparan is a small peptide composed of 14 amino acid residues, and Malencik and Anderson have reported a strong binding constant of mastoparan to calmodulin (4).
KeywordsMyosin Light Chain Kinase Binding Curve Narrow Concentration Range Chicken Gizzard Myosin Light Chain Kinase Activity
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- 11.M. Ikura, N. Hasegawa, K. Hikichi, S. Aimoto, M. Yazawa and K. Yagi, 113Cd-NMR Evidence for cooperative interaction between the amino-and carboxyl-terminal domains of calmodulin, in preparationGoogle Scholar