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Updated: Feb 1, 2026

Kinase Inhibitor Screening In Self-assembled Human Protein Microarrays
Published on: October 23, 2019
Multiple isoforms of a protein kinase C inhibitor (KCIP-1/14-3-3) from sheep brain. Amino acid sequence of
A Toker1, L A Sellers, B Amess
1Laboratory of Protein Structure, National Institute for Medical Research, Mill Hill, London, England.
Abstract:
A potent inhibitor of protein kinase C (PKC), inhibitor protein-1 (KCIP-1), isolated from sheep brain has been shown to consist of eight isoforms by reverse-phase HPLC. Direct protein sequence analysis has revealed these to be the same as those of 14-3-3 protein, described as an activator of tyrosine and tryptophan hydroxylases involved in neurotransmitter biosynthesis. The N-termini of KCIP-1 isoforms were shown to be acetylated, and secondary structure predictions revealed a high degree of alpha-helix with an amphipathic nature. KCIP-1 showed no inhibitory activity towards protein kinase M (the catalytic fragment of PKC) and had no effect on the activities of three other protein kinases, cAMP-dependent protein kinase, Ca2+/calmodulin-dependent protein kinase II and casein kinase 2. Four forms of KCIP-1 were shown to be substrates for PKC in vitro, but none were phosphorylated by the other protein kinases mentioned above.
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