Abstract
A retro-inverso, TAT-like peptide wherein lysine residues are replaced with cysteine residues bearing a disulfide-linked cysteamine group is found to engage in thiol-disulfide exchange with cysteine. These peptides are transported into cells and localize to lysosomes. Cellular uptake is enhanced in peptides bearing two cysteamine groups over those with one or none, by factors of approximately 1.5 and 12, respectively.