Phosphorylation of the Protein Encoded by the First Open Reading Frame of the MDG4 Transposable Element (gypsy) by Homologous and Heterologous Casein Kinases Type 2

M. A. Malikova¹, B. V. Syomin², and A. S. Stepanov^1*

¹Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, Moscow, 117071 Russia; fax: (095) 954-2732; E-mail: inbio@glas.apc.org

²Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, ul. Vavilova 32, Moscow, 117984 Russia; fax: (095) 135-1405; E-mail: syomin@genome.eimb.relarn.ru

^* To whom correspondence should be addressed.

Received April 7, 2000; Revision received June 22, 2000

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Homogeneous casein kinase type 2 (CK2) was obtained from oocytes of Rana temporaria and cells of Drosophila melanogaster by chromatography on heparin-Sepharose, phosphocellulose, and Mono Q columns using a Pharmacia FPLC system. The procedure was first successfully used for the purification of CK2 from the Drosophila melanogaster cell culture. It has been shown that the protein encoded by the first open reading frame (ORF) of the gypsy transposable element (MDG4) is an effective protein substrate both for homologous and heterologous CK2 from the oocytes of Rana temporaria in vitro. Both enzymes catalyze the incorporation of two moles of phosphate per mole of protein. The K_m and V_max values for the reaction catalyzed by CK2 from the Drosophila cell culture were 32.5 ± 2.1 nM and 70.97 ± 1.89 nmol/min per µg, respectively, and for CK2 from oocytes, these values were 37.6 ± 2.8 nM and 66.02 ± 2.15 nmol/min per µg, respectively.

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Key words: casein kinase type 2, retrotransposon, gypsy, GAG, phosphorylation substrates

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