Biochemical characterization of cholesterol-3-sulfate as the sole effector for the phosphorylation of HMG1 by casein kinase I in vitro.
Phosphorylation of high mobility group protein 1 (HMG1) by casein kinase I (CK-I) and potent effectors (inhibitors and activators) of this phosphorylation were investigated in vitro. We found that (i) CK-I phosphorylates specifically threonine residues on HMG1 when incubated with cholesterol-3-sulfate (CH-3S), but no phosphorylation of HMG1 is detected in the presence of other cholesterol related compounds or their sulfated derivatives; (ii) this phosphorylation is selectively inhibited by heparin, but stimulated significantly by 3',4',7-trihydroxy-isofavone at low doses (0.1-3 microM); and (iii) CH-3S directly induces a drastic conformational change in HMG1. The latter finding provides a mechanism to explain how CH-3S alone can induce the phosphorylation of HMG1 by CK-I in vitro.
Laboratory of Genetical Biochemistry, Graduate School of Medical Sciences, Kitasato University, Kitasato 1-15-1, Sagamihara, 228-8555, Japan.
M
M
Okano
S
S
Kano
H
H
Munakata
K
K
Ohtsuki
D000818:Animals; D047388:Casein Kinases; D002417:Cattle; D002788:Cholesterol Esters / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005419:Flavonoids; D006493:Heparin / Q000494:pharmacology; D006609:High Mobility Group Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010636:Phenols / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010769:Phosphothreonine / Q000378:metabolism; D011108:Polymers / Q000494:pharmacology; D059808:Polyphenols; D011487:Protein Conformation / Q000187:drug effects; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*
D002788:Cholesterol Esters; D005419:Flavonoids; D006609:High Mobility Group Proteins; D010636:Phenols; D011108:Polymers; D059808:Polyphenols; D047428:Protein Kinase Inhibitors; D010769:Phosphothreonine; D006493:Heparin; D011494:Protein Kinases; D047388:Casein Kinases; C007045:cholesteryl sulfate