J. Biol. Chem., Vol. 255, Issue 10, 4589-4594, 05, 1980
Two naturally occurring inhibitors of nuclear protein kinase
F Farron-Furstenthal
2Two types of protein kinase inhibitors present in rat liver nuclei have
been partially purified and characterized. They are specific for the
nuclear enzymes, being inert toward the protein kinases in the cytosol. One
inhibitor is a 150,000 dalton, heat-labile, acidic protein; the other is a
family of two oligonucleotides. Inhibitory activity in crude extracts
becomes measurable only after complete removal of protein kinase activity
by affinity chromatography (Farron- Furstenthal, F., and Lightholder, J.R.
(1977) FEBS Lett. 84, 313). Initial separation of the inhibitor protein
from the oligonucleotide inhibitors was achieved by filtration through an
Amicon pressure cell. Further purification of the inhibitor protein was
obtained by chromatography on ion exchangers and Bio-Gel. The
oligonucleotides were purified by DEAE-cellulose chromatography and paper
electrophoresis. The effects of the two types of inhibitors are additive.
The 170 to 200% recovery of protein kinase activity after removal of the
inhibitors from the initial extracts suggests that the inhibitors
contribute in a quantitatively significant measure to the regulation of
nuclear protein phosphorylation.
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