Arginine carrier peptide bearing Ni(II) chelator to promote cellular uptake of histidine-tagged proteins.

Arginine-rich peptide-mediated protein delivery into living cells is a novel technology for controlling cell functions with therapeutic potential. In this report, a novel approach for the intracellular delivery of histidine-tagged proteins was introduced where a Ni(II) chelate of octaarginine peptide bearing nitrilotriacetic acid [R8-NTA-Ni(II)] was used as a membrane-permeable carrier molecule. Significant internalization of histidine-tagged enhanced green fluorescent protein (EGFP) into HeLa cells was observed by confocal microscopic observation in the presence of R8-NTA-Ni(II). Nuclear condensation characteristic in apoptotic cell death was also induced in the cells treated with a histidine-tagged apoptosis-inducing peptide [pro-apoptotic domain peptide (PAD)], indicating that the cargo molecules really went through the membrane to reach the cytosol. The apoptosis-inducing activity of the peptide thus delivered was compared with that of the PAD peptide covalently connected with the octaarginine peptide.