Casein kinase II protein kinase is bound to lamina-matrix and phosphorylates lamin-like protein in isolated pea nuclei.
A casein kinase II (CK II)-like protein kinase was identified and partially isolated from a purified envelope-matrix fraction of pea (Pisum sativum L.) nuclei. When [gamma-32P]ATP was directly added to the envelope-matrix preparation, the three most heavily labeled protein bands had molecular masses near 71, 48, and 46 kDa. Protein kinases were removed from the preparation by sequential extraction with Triton X-100, EGTA, 0.3 M NaCl, and a pH 10.5 buffer, but an active kinase still remained bound to the remaining lamina-matrix fraction after these treatments. This kinase had properties resembling CK II kinases previously characterized from animal and plant sources: it preferred casein as an artificial substrate, could use GTP as efficiently as ATP as the phosphoryl donor, was stimulated by spermine, was calcium independent, and had a catalytic subunit of 36 kDa. Some animal and plant CK II kinases have regulatory subunits near 29 kDa, and a lamina-matrix-bound protein of this molecular mass was recognized on immunoblot by anti-Drosophila CK II polyclonal antibodies. Also found associated with the envelope-matrix fraction of pea nuclei were p34cdc2-like and Ca(2+)-dependent protein kinases, but their properties could not account for the protein kinase activity bound to the lamina. The 71-kDa substrate of the CK II-like kinase was lamin A-like, both in its molecular mass and in its cross-reactivity with anti-intermediate filament antibodies. Lamin phosphorylation is considered a crucial early step in the entry of cells into mitosis, so lamina-bound CK II kinases may be important control points for cellular proliferation.
Li
H
H
Department of Botany, University of Texas, Austin 78713.
Roux
S J
SJ
D000595:Amino Acid Sequence; D047390:Casein Kinase II; D002451:Cell Compartmentation; D007887:Fabaceae; D034904:Lamin Type A; D034882:Lamins; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D015530:Nuclear Matrix / Q000201:enzymology*; D009687:Nuclear Proteins / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D010946:Plants, Medicinal; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*
D034904:Lamin Type A; D034882:Lamins; D009687:Nuclear Proteins; D010455:Peptides; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases