Screening for selective protein inhibitors using IANUS peptide array.

The IANUS (Induced orgANization of strUcture by matrix-assisted togethernesS) peptide array was build up on a hypothesis that two peptides from two interacting protein epitopes are also able to interact when immobilized on a solid support. This peptide-peptide interactions can be visualized by FRET effects caused by close proximity of fluorescent labeled peptide chains. The biggest advantage of this low-resolution method is that no soluble protein probe or selective antibodies are needed. We applied the IANUS peptide array to screen for peptides from a phospatase Calcineurin (CaN) that binds to regulatory domain of the nuclear factor of activated T cells (NFAT). Peptides derived from the IANUS-library hits were tested for their ability to suppress i) the NFAT dephosphorylation by CaN, ii) the NFkB dephosphorylation by CaN, and iii) the CaN phosphatase activity. The best hit, peptide FPSLITIFSAPNYLDVYN, appeared to be a protease-resistant and cell-permeable NFAT inhibitor.