Phosphorylation of serine 833 in cytoplasmic domain of low density lipoprotein receptor by a high molecular weight enzyme resembling casein kinase II

A. Kishimoto, M. S. Brown, C. A. Slaughter, J. L. Goldstein

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A soluble protein kinase that phosphorylates the last serine residue (Ser-833) in the cytoplasmic domain of the low density lipoprotein (LDL) receptor was purified about 1300-fold from the cytosol of bovine adrenal cortex. The LDL receptor kinase shared several properties with casein kinase II: 1) use of either GTP or ATP; 2) phosphorylation of a typical casein kinase II recognition sequence in the LDL receptor (a serine followed by a cluster of three negatively charged amino acids); and 3) inhibition by heparin. The LDL receptor kinase differed from classic casein kinase II in the following respects: 1) its apparent molecular weight on gel filtration was ~ 500,000 as opposed to the usual molecular weight of 130,000 for casein kinase II; 2) its affinity for the LDL receptor (apparent K(m) ~ 5 nM) was much greater than its affinity for casein (~ 10 μM); and 3) its activity was inhibited by polylysine, an agent that stimulates casein kinase II. The physiologic role of this unusual kinase, if any, is unknown.

Original languageEnglish (US)
Pages (from-to)1344-1351
Number of pages8
JournalJournal of Biological Chemistry
Issue number3
Publication statusPublished - 1987


ASJC Scopus subject areas

  • Biochemistry

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