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A Casein Kinase‐Like Kinase Phosphorylates β‐Tubulin and May Be a Microtubule‐Associated Protein
Author(s) -
Crute Barbara E.,
Buskirk Robert G.
Publication year - 1992
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.1471-4159.1992.tb10089.x
Subject(s) - casein kinase 2 , tubulin , microtubule , phosphorylation , kinase , protein kinase a , cytosol , biochemistry , biology , microbiology and biotechnology , chemistry , cyclin dependent kinase 2 , enzyme
The hypothesis that casein kinase II (CKII) is a microtubule‐associated protein kinase was investigated using a neuronal cell line and bovine brain. Heparin, an inhibitor of CKII, inhibited the phosphorylation of a PC12 cytosolic protein whose molecular weight was similar to that of β‐tubulin. Partially purified PC12 CKII was immunoreactive to an antibody directed against bovine CKII and was able to phosphorylate purified β‐tubulin in a heparin‐inhibitable manner when the concentration of tubulin was less than 50 μg/ml. To better determine if CKII is a microtubule‐associated protein kinase, bovine brain tubulin was chromatographed on FPLC Mono Q and phosphocellulose columns. Several tubulin casein kinase (TCK) activities were apparent. All TCK activities phosphorylated tubulin and casein, but none was able to phosphorylate the CKII‐specific synthetic peptide RRREEETEEE. One of these TCK fractions was immunoreactive to the antibody directed against CKII, and this antibody labeled a 50‐kDa molecular mass band that had a molecular mass distinctly different from those of the subunits of CKII. Thus, we suggest that a CKII‐like protein, but not CKII, might be a microtubule‐associated protein.