Protein kinase CKII interacts with and phosphorylates the SAG protein containing ring-H2 finger motif.
To investigate the biological function of CKII, we have identified proteins that interact with the subunits of CKII using the yeast two-hybrid system. Here we report that SAG, an antioxidant protein containing Ring-H2 finger motif, is a cellular partner associating with the beta subunit of CKII. SAG does not interact with the alpha subunit of CKII. Analysis of SAG deletion mutants indicates that the Ring-H2 motif of SAG is necessary and sufficient for its binding to the beta subunit of CKII. Recombinant SAG can be phosphorylated by CKII in vitro, providing evidence that the beta subunit mediates the interaction of CKII enzyme with substrate proteins. Overlay experiment shows that SAG and the beta subunit of CKII associate directly in vitro and that CKII-mediated phosphorylation of SAG does not affect the interaction between SAG and the beta subunit of CKII. Northern blot analysis indicates that both SAG and the beta subunit of CKII were relatively rich in human heart, liver, skeletal muscle, and pancreas, but were detected in only trace amounts in brain, placenta, and lung. Our present results suggest that CKII may play a role in the regulation of SAG function.
Son
M Y
MY
Department of Microbiology, Kyungpook National University, Taegu, 702-701, Korea.
Park
J W
JW
Kim
Y S
YS
Kang
S W
SW
Marshak
D R
DR
Park
W
W
Bae
Y S
YS
D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D005260:Female; D016166:Free Radical Scavengers / Q000737:chemistry* / Q000378:metabolism*; D015723:Gene Library; D006367:HeLa Cells; D006801:Humans; D008099:Liver / Q000378:metabolism; D046911:Macromolecular Substances; D018482:Muscle, Skeletal / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009206:Myocardium / Q000378:metabolism; D016366:Open Reading Frames; D009928:Organ Specificity; D010179:Pancreas / Q000378:metabolism; D010766:Phosphorylation; D011247:Pregnancy; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development; D017384:Sequence Deletion; D044767:Ubiquitin-Protein Ligases; D016335:Zinc Fingers
D016166:Free Radical Scavengers; D046911:Macromolecular Substances; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; C118307:RNF7 protein, human; D044767:Ubiquitin-Protein Ligases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases