FKBP, the binding protein for the immunosuppressive drug, FK-506, is not an inhibitor of protein kinase C activity

John Cryan, Shirley H.Y. Hung, Gregory Wiederrecht, Nolan H. Sigal, John J. Siekierka

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Recently, the amino acid sequence of a 12 Kd endogenous protein inhibitor of protein kinase C (PKC-I 2) has been shown to be identical to that of the 12 KDa receptor for the immunosuppressive drug, FK-506. In view of this observation we examined the effects of recombinant and native human FKBP on protein kinase C (PKC) activity. FKBP, at molar concentrations up to 1900-fold over that of PKC, failed to inhibit PKC phosphorylation of histone H1 and failed to block the auto-phosphorylation of PKC. Interestingly, FKBP is phosphorylated by PKC in these reactions. The phosphorylation of FKBP by PKC appears to be specific since the catalytic subunit of cAMP-dependent protein kinase fails to phosphorylate the binding protein. Our results fail to support a role for FKBP as an inhibitor of protein kinase C.

Original languageEnglish
Pages (from-to)846-852
Number of pages7
JournalBiochemical and Biophysical Research Communications
Issue number2
StatePublished - 31 Oct 1991


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