Development of Cell-Penetrating ZIP Tag-Probe Systems for Fluorescent Imaging of Protein Dynamics in Cells

Fuorogenic probes are useful because they can suppress noise associated with background emission. A new tag-probe pair with fluorogenic activity using the leucine zipper assembly was developed. Probe peptides were designed as α-helix peptides with a solvatochromic fluorescent dye. To enable the cell penetration of the probe peptide, addition of a cell penetrating peptide (CPP) sequence, octaarginine was tested. A probe peptide with octaarginine at C-terminus was shown to maintain high affinity to the tag peptide. Pre-treatment of cells with 1-pyrenebutyrate enhanced distribution of the probe peptide to cytoplasm. It was shown that the concentration of the probe peptide could be reduced to 0.1 μM. The system is highly compatible to virtually any proteins because of its simplicity in handling.