Calmodulin fragments can not activate target enzymes.
Under conditions where nM level of calmodulin was able to show full activation of myosin light chain kinase and cyclic-nucleotide phosphodiesterase, the fragments of calmodulin at concentrations as high as 20 microM failed to activate these enzymes in the presence of Ca2+. The fragments tested were Ala1-Lys75 (F12), Ala1-Arg74 (F12'), Lys75-Lys148 (F34'), Met76-Lys148 (F34'), Asp78-Lys148 (F34), Ala1-Arg106 (F123), and His107-Lys148 (F4). Purification of the proteolytic fragments through HPLC was necessary to remove contaminant calmodulin. Among the fragments, that corresponding to the C-terminal half domain inhibited myosin light chain kinase activity with the inhibition constant of 13 microM. The integrated structure of calmodulin consisting of N-terminal half domain, C-terminal half domain, and the linker peptide was indispensable for the enzyme activation. We discuss the functions of the two structural domains (N-domain and C-domain) in the activation of various enzymes.
Minowa
O
O
Department of Chemistry, Faculty of Science, Hokkaido University.
Yazawa
M
M
Sobue
K
K
Ito
K
K
Yagi
K
K
D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000378:metabolism*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005260:Female; D008297:Male; D008974:Mollusca; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D014357:Trypsin / Q000378:metabolism
D000596:Amino Acids; D002147:Calmodulin; D010446:Peptide Fragments; D009219:Myosin-Light-Chain Kinase; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D014357:Trypsin; D002118:Calcium