Phage display identifies thioredoxin and superoxide dismutase as novel protein kinase C-interacting proteins: thioredoxin inhibits protein kinase C-mediated phosphorylation of histone.

Using phage display we identify the redox proteins thioredoxin and superoxide dismutase (SOD) as novel protein kinase C (PKC)-interacting proteins. Overlay assays demonstrated that PKC bound to immobilized thioredoxin, providing supporting evidence for the phage display results. Kinase assays demonstrated that SOD and thioredoxin were not direct substrates for PKC but that both proteins blocked autophosphorylation of PKC. Moreover, thioredoxin inhibited PKC-mediated phosphorylation of histone (IC(50) of approx. 20 ng/ml).