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Eukaryotic Cell, December 2003, p. 1220-1233, Vol. 2, No. 6
1535-9778/03/$08.00+0     DOI: 10.1128/EC.2.6.1220-1233.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Molecular Identification of a Calcium-Inhibited Catalytic Subunit of Casein Kinase Type 2 from Paramecium tetraurelia

Daniel Vetter,1 Roland Kissmehl,1* Tilman Treptau,1 Karin Hauser,1 Josef Kellermann,2 and Helmut Plattner1

Department of Biology, University of Konstanz, 78457 Konstanz,1 Toplab, Gesellschaft für Angewandte Biotechnologie GmbH, 82152 Martinsried, Germany2

Received 14 April 2003/ Accepted 27 August 2003

We have previously described the occurrence in Paramecium of a casein kinase (CK) activity (EC 2.7.1.37) with some unusual properties, including inhibition by Ca2+ (R. Kissmehl, T. Treptau, K. Hauser, and H. Plattner, FEBS Lett. 402:227-235, 1995). We now have cloned four genes, PtCK2{alpha}1 to PtCK2{alpha}4, all of which encode the catalytic {alpha} subunit of type 2 CK (CK2) with calculated molecular masses ranging from 38.9 to 39.4 kDa and pI values ranging from 8.8 to 9.0. They can be classified into two groups, which differ from each other by 28% on the nucleotide level and by 18% on the derived amino acid level. One of them, PtCK2{alpha}3, has been expressed in Escherichia coli and characterized in vitro. As we also have observed with the isolated CK, the recombinant protein preferentially phosphorylates casein but also phosphorylates some Paramecium-specific substrates, including the exocytosis-sensitive phosphoprotein pp63/parafusin. Characteristically, Ca2+ inhibits the phosphorylation at elevated concentrations occurring during stimulation of a cell. Reconstitution with a recombinant form of the regulatory subunit from Xenopus laevis, XlCK2ß, confirms Ca2+ sensitivity also under conditions of autophosphorylation. This is unusual for CK2 but correlates with the presence of two EF-hand calcium-binding motifs, one of which is located in the N-terminal segment essential for constitutive activity, as well as with an aberrant composition of normally basic domains recognizing acidic substrate domains. Immunogold localization reveals a considerable enrichment in the outermost cell cortex layers, excluding cilia. We discuss a potential role of this Ca2+-inhibited PtCK2{alpha} species in a late step of signal transduction.

* Corresponding author. Mailing address: Department of Biology, University of Konstanz, P.O. Box 5560, 78457 Konstanz, Germany. Phone: 49-7531-88-3712. Fax: 49-7531-88-2245. E-mail: Roland.Kissmehl{at}uni-konstanz.de.

Eukaryotic Cell, December 2003, p. 1220-1233, Vol. 2, No. 6
1535-9778/03/$08.00+0     DOI: 10.1128/EC.2.6.1220-1233.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Kissmehl, R., Kruger, T. P., Treptau, T., Froissard, M., Plattner, H. (2006). Multigene Family Encoding 3',5'-Cyclic-GMP-Dependent Protein Kinases in Paramecium tetraurelia Cells. Eukaryot Cell 5: 77-91 [Abstract] [Full Text]  


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