SV40 Nuclear Transport Signal Peptide Analog, H-Cys-Gly-Tyr-Gly-Pro-Lys-Lys-Lys-Arg-Lys-Val-Gly-Gly-OH, 104914-40-1, C60H104N20O15S, Mr 1377.68, 5mg. C-G-Y-G-P-K-K-K-R-K-V-G-G, NLS. NLS, cell-penetrating peptide containing 7 amino acids homologous to the SV40 T antigen, was capable of inducing the transport of several carrier proteins to the nucleus. The terminal cysteine permits the attachment of this peptide to any protein using a heterobifunctional crosslinking reagent. Coupling to plasmid DNA has also been realized by M.G.Sebastyén and coworkers. Heterodimerization of TAT and NLS yields an even more effective transfecting peptide.