Budding and Fission Yeast Casein Kinase-I Isoforms Have Dual-Specificity Protein-Kinase Activity

Hoekstra, M. F., Dhillon, N., Carmel, G., Demaggio, A. J., Lindberg, R. A., Hunter, T., Kuret, J. (August 1994) Budding and Fission Yeast Casein Kinase-I Isoforms Have Dual-Specificity Protein-Kinase Activity. Molecular Biology of the Cell, 5 (8). pp. 877-886. ISSN 1059-1524

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URL: http://www.ncbi.nlm.nih.gov/pubmed/7803855
DOI: 10.1091/mbc.5.8.877


We have examined the activity and substrate specificity of the Saccharomyces cerevisiae Hrr25p and the Schizosaccharomyces pombe Hhp1, Hhp2, and Cki1 protein kinase isoforms. These four gene products are isotypes of casein kinase I (CKI), and the sequence of these protein kinases predicts that they are protein serine/threonine kinases. However, each of these four protein kinases, when expressed in Escherichia coli in an active form, was recognized by anti-phosphotyrosine antibodies. Phosphoamino acid analysis of P-32-labeled proteins showed phosphorylation on serine, threonine, and tyrosine residues. The E. coli produced forms of Hhp1, Hhp2, and Cki1 were autophosphorylated on tyrosine, and both Hhp1 and Hhp2 were capable of phosphorylating the tyrosine-protein kinase synthetic peptide substrate polymer poly-E(4)Y(1). Immune complex protein kinases assays from S. pombe cells showed that Hhp1-containing precipitates were associated with a protein-tyrosine kinase activity, and the Hhp1 present in these immunoprecipitates was phosphorylated on tyrosine residues. Although dephosphorylation of Hhp1 and Hhp2 by Ser/Thr phosphatase had little effect on the specific activity, tyrosine dephosphorylation of Hhp1 and Hhp2 caused a 1.8-to 3.1-fold increase in the Km for poly-E(4)Y(1) and casein. These data demonstrate that four different CKI isoforms from two different yeasts are capable of protein-tyrosine kinase activity and encode dual-specificity protein kinases.

Item Type: Paper
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > enzymes > kinase
organism description > yeast
CSHL Authors:
Communities: CSHL labs > Stillman lab
Depositing User: Matt Covey
Date: August 1994
Date Deposited: 26 Aug 2015 15:22
Last Modified: 26 Aug 2015 15:22
PMCID: PMC301108
Related URLs:
URI: https://repository.cshl.edu/id/eprint/31403

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