In the previous study, the artificial cationic coiled-coil protein, CCPC 140, was designed to have the structural frame of human skeletal muscle α-tropomyosin. This CCPC 140 showed superior cell-penetrating activity. Looking at thermal melting profiles of circular dichroism, although all the amino acid residues at the coiled-coil intramolecular interface in heptad repeat were conserved, the Tm of CCPC 140 was much higher than that of α-tropomyosin. This indicates that the residues at outer surface of coiled-coil motif can be a determinant of structure stability. In this study, I explored a novel mechanism for structure stabilization on coiled-coil proteins.