Mg2+ inhibits formation of 4Ca(2+)-calmodulin-enzyme complex at lower Ca2+ concentration. 1H and 113Cd NMR studies.
Our previous 1H NMR studies indicated that when mastoparan (MP) is added to Ca(2+)-half-saturated calmodulin (2Ca(2+)-CaM) in the absence of Mg2+ ions, Ca2+ ions transfer from the C-terminal-half domain of CaM not interacting with MP to the N-terminal-half domain of CaM interacting with MP at lower MP concentrations (Ohki, S., Yazawa, M., Yagi, K., and Hikichi, K. (1991b) J. Biochem. (Tokyo) 110, 737-742). As a consequence, the active form of 4Ca(2+)-CaM.MP complex is formed. In the present study, we studied the effect of Mg2+ ions on Ca2+ transfer. In the presence of Mg2+ ions, such Ca2+ transfer does not occur. The effects of Mg2+ ions are also studied by observing 113Cd NMR in the presence of M13, the 26-residue peptide of the CaM-binding region of myosin light chain kinase. The 113Cd NMR results show that Mg2+ ions prevent to form the active complex. Mg2+ plays an important role as an inactivating factor to CaM.
Department of Polymer Science, Faculty of Science, Hokkaido University, Sapporo, Japan.
S
S
Ohki
U
U
Iwamoto
S
S
Aimoto
M
M
Yazawa
K
K
Hikichi
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002104:Cadmium; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006859:Hydrogen; D036341:Intercellular Signaling Peptides and Proteins; D007554:Isotopes; D008274:Magnesium / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008969:Molecular Sequence Data; D008974:Mollusca; D010446:Peptide Fragments; D010455:Peptides / Q000138:chemical synthesis; D011485:Protein Binding; D013737:Testis; D014862:Wasp Venoms / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002147:Calmodulin; D036341:Intercellular Signaling Peptides and Proteins; D007554:Isotopes; D010446:Peptide Fragments; D010455:Peptides; D014862:Wasp Venoms; D002104:Cadmium; C037500:mastoparan; D006859:Hydrogen; D008274:Magnesium; D002118:Calcium