Specific and direct binding of protein kinase C to an immobilized tamoxifen analogue.
We have previously demonstrated that tamoxifen and related triphenylethylene compounds are potent inhibitors of protein kinase C (PKC). The present study demonstrates that PKC binds specifically and reversibly to the antiestrogen N-didesmethyltamoxifen when the drug is coupled to CNBr-activated agarose through its primary amine, in the absence of lipid and other cofactors of the enzyme. PKC did not bind to 4-hydroxytamoxifen, which had been immobilized on epoxy-activated Sepharose through its hydroxyl moiety. This shows that the binding of PKC to immobilized N-didesmethyltamoxifen was not merely due to hydrophobic interactions, since N-didesmethyltamoxifen and 4-hydroxytamoxifen have nearly identical hydrophobicities. These results demonstrate that PKC has specific triphenylethylene-binding sites, which may mediate the inhibition of PKC activity by these antiestrogens.
O'Brian
C A
CA
Comprehensive Cancer Center, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
Housey
G M
GM
Weinstein
I B
IB
D000345:Affinity Labels; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002846:Chromatography, Affinity; D007536:Isomerism; D007700:Kinetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D013329:Structure-Activity Relationship; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000378:metabolism
D000345:Affinity Labels; D013629:Tamoxifen; D011493:Protein Kinase C; D002118:Calcium