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Ca 2+ – and Calmodulin‐Dependent Phosphorylation of Microtubule‐Associated Protein 2 and t Factor, and Inhibition of Microtubule Assembly
Author(s) -
Yamamoto Hideyuki,
Fukunaga Kohji,
Tanaka Etsuro,
Miyamoto Eishichi
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb09060.x
Subject(s) - microtubule , calmodulin , phosphorylation , microbiology and biotechnology , microtubule associated protein , chemistry , biophysics , biology , biochemistry , enzyme
Microtubule‐associated proteins (MAPs) were phosphorylated by a Ca 2+ – and calmodulin‐dependent protein kinase from rat brain cytosol. The maximal amount of phosphate incorporated into MAPs was 25 nmol of phosphate/mg protein. A K a value of the enzyme for calmodulin was 57.0 n M , with MAPs as substrates. Among MAPs, MAP2 and t factor were phosphorylated in a Ca 2 + ‐and calmodulin‐dependent manner. The phosphorylation of MAPs led to an inhibition of microtubule assembly in accordance with its degree. This reaction was dependent on addition of the enzyme, Ca 2+ , and calmodulin, and had a greater effect on the initial rate of microtubule assembly rather than on the final extent. The critical tubulin concentration for microtubule assembly was unchanged by the MAPs phosphorylation. Therefore assembly and disassembly of brain microtubule are regulated by the Ca 2+ ‐ and calmodulin‐dependent protein kinase that requires only a nanomolar concentration of calmodulin for activation.