Abstract
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 language | English (US) |
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Pages (from-to) | 1344-1351 |
Number of pages | 8 |
Journal | Journal of Biological Chemistry |
Volume | 262 |
Issue number | 3 |
State | Published - 1987 |
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology