Pep-1 is one of the synthetic cell-penetrating peptides (CPPs), which has been successfully used to deliver a variety of proteins and other biopharmaceutical macromolecules into cells in a non-disruptive way. It is a CPP with primary amphipathicity (i.e amphipathicity resulting from the amino acid sequence itself, not from the folding structure) that comprises a tryptophan-rich so-called ‘hydrophobic’ domain, a hydrophilic domain derived from an NLS (nuclear localization signal) of SV40 (simian virus 40) large T-antigen, and a spacer between them. A cysteamine group is present at the C-terminus. The presence of cysteamine group in C terminal seems to play a crucial role in the delivery efficiency of cargoes into cells.
Henriques, S. et al. FEBS Letters Vol. 579, 4498 (2005).