Characteristics of a nuclear protein kinase from rat epididymis.
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Date
1984-03
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Abstract
Purified rat epididymal nuclei possess a cyclic AMP-independent protein kinase
activity that phosphorylates of casein. The enzymic activity was solubilized by treating intact
nuclei with 1 M (NH4)2SO4. One major peak of kinase activity was obtained when the
solubilized enzyme preparation was subjected to diethylaminoethyl-Sephadex chromatography.
The activity of the kinase was dependent on a bivalent metal ion such as Mg2+, Co2+,
Ca2+ or Mn2+. NaCl (0·3 M) caused a further activation (approx. 200%) of the metal (Co2+)-
dependent enzyme. The apparent Km values of the enzyme for casein, ATP and Co2+ are
approx. 0·6 mg/ml, 10 μΜ and 2·2 mM respectively. The enzyme was maximally active at pH
5·5. The enzyme showed high specificity for phosphorylation of the acidic protein casein but
did not phosphorylate basic proteins, such as histones and protamine. The properties of the
nuclear protein kinase were clearly different from those of the cytosolic enzymes previously
characterized.
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Keywords
Protein kinase, epididymis, nuclei, protein phosphorylation
Citation
Biswas Rupamanjari, Majumder Gopal C. Characteristics of a nuclear protein kinase from rat epididymis. Journal of Biosciences. 1984 Mar; 6(1): 69-77.