Screening of a library of T7 phage-displayed peptides identifies alphaC helix in 14-3-3 protein as a CBP501-binding site

Department of Applied Biological Sciences, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Bioorganic & medicinal chemistry (Impact Factor: 2.79). 12/2011; 19(23):7049-56. DOI: 10.1016/j.bmc.2011.10.004
Source: PubMed

ABSTRACT CBP501 is a chemically modified peptide composed of twelve unnatural d-amino acids, which inhibits Chk kinase and abrogates G2 arrest induced by DNA-damaging agents. Here we identified an alphaC helix in 14-3-3 protein as a CBP501-binding site using T7 phage display technology. An affinity selection of T7 phage-displayed peptide using biotinylated CBP501 identified a 14-mer peptide NSDCIISRKIEQKE. This peptide sequence showed similarity to a portion of the alphaC helix of human 14-3-3ε, suggesting that CBP501 may bind to this region. Surface plasmon resonance (SPR) and ELISA demonstrated that CBP501 interacts with 14-3-3ε specifically at the screen-guided region. An avidin-agarose bead pull-down assay showed that CBP501 also binds to other 14-3-3 isoforms in Jurkat cells. Among the other known Chk kinase inhibitors tested, CBP501 showed the strongest affinity for 14-3-3ε. Thus, we conclude that in addition to the direct inhibition of Chk kinase activity, CBP501 directly binds to cellular 14-3-3 proteins through alphaC helix.

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Yoichi Takakusagi