Copurification of casein kinase II with 20 S proteasomes and phosphorylation of a 30-kDa proteasome subunit.
The 20 S proteasome is a multicatalytic protease that has been implicated in several processes including ATP/ubiquitin-dependent proteolysis. However, the ATP requirement(s) related to proteasome function is undefined. We demonstrate that a protein kinase activity copurifies through multiple steps utilized to isolate latent 20 S proteasomes from human erythrocytes. The kinase phosphorylates serine residues within a single 30-kDa proteasome subunit. The activity is not sensitive to cyclic AMP or protein kinase inhibitor, indicating that it is not a cyclic AMP-dependent kinase. It is sensitive to nanomolar levels of heparin and is able to utilize both ATP and GTP as phosphodonors, similar to casein kinase II activity. Moreover, a polyclonal antibody specific for casein kinase II recognizes the alpha' subunit of casein kinase II in the 20 S preparation and specifically immunoprecipitates the proteasome-phosphorylating activity. These characteristics suggest that the proteasome kinase is similar or identical to casein kinase II. It is suggested that phosphorylation of the 30-kDa proteasome subunit by casein kinase II may be involved in regulating the activity and/or assembly of proteasome complexes.
Ludemann
R
R
Department of Cell Biology and Anatomy, New York Medical College, Valhalla 10595.
Lerea
K M
KM
Etlinger
J D
JD
D015153:Blotting, Western; D047390:Casein Kinase II; D003546:Cysteine Endopeptidases / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D006801:Humans; D009097:Multienzyme Complexes / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D010449:Peptide Mapping; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D017346:Protein Serine-Threonine Kinases / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism
D009097:Multienzyme Complexes; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex