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Phosphorylation of Purified Rat Striatal Tyrosine Hydroxylase by Ca 2+ /Calmodulin‐Dependent Protein Kinase II: Effect of an Activator Protein
Author(s) -
Atkinson Janet,
Richtand Neil,
Schworer Charles,
Kuczenski Ronald,
Soldering Thomas
Publication year - 1987
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.1471-4159.1987.tb10016.x
Subject(s) - protein kinase a , tyrosine hydroxylase , biochemistry , protein phosphorylation , phosphorylation , activator (genetics) , mitogen activated protein kinase kinase , tyrosine , biology , map2k7 , chemistry , cyclin dependent kinase 2 , microbiology and biotechnology , enzyme , gene
The phosphorylation of tyrosine hydroxylase, purified from rat striatum, was investigated using purified Ca 2+ /calmodulin (CaM)‐dependent protein kinase II. This kinase catalyzed the Ca 2+ ‐dependent incorporation of up to 0.8 mol 32 PO 4 /mol tyrosine hydroxylase subunit (62 kilo‐daltons). Reverse‐phase high‐performance liquid chroma‐tography mapping of tryptic 32 P‐peptides established that the Ca 2+ /CaM‐dependent protein kinase II phosphorylated a different serine residue than was phosphorylated by the cyclic AMP‐dependent protein kinase. Limited proteolysis sequentially reduced the subunit M r from 62 to 59 kilodaltons and finally to 57 kilodaltons, resulting in loss of the site phosphorylated by the Ca 2+ /CaM‐dependent protein kinase II, but not the site phosphorylated by the cyclic AMP‐dependent protein kinase. Phosphorylation by the Ca 2+ / CaM‐dependent protein kinase II had little direct effect on the kinetic properties of tyrosine hydroxylase, but did convert it to a form that could be activated twofold by addition of an activator protein. This heat‐labile activator protein increased the V max without affecting the K m for the pterin cofactor. This effect was specific in that the activator protein was without effect on nonphosphorylated tyrosine hydroxylase or on tyrosine hydroxylase phosphorylated by the cyclic AMP‐dependent protein kinase. These results are consistent with the hypothesis that the „ V max ‐type” activation of tyrosine hydroxylase observed upon depolarization of neural and adrenal tissues may be mediated by the Ca 2+ / CaM‐dependent protein kinase II.