Poor membrane permeability of proteins is a major limitation of protein therapy. In a previous study, we showed that the minimal sequence required for effi-cient transduction of Tat-GFP is the basic domain from 49-57 of HIV-1 Tat called the protein transduc-tion domain (PTD. Here we have generated HIV-1 Tat PTD GFP fusion proteins in which HIV-1 Tat PTD is fused with the N- and/or C-termini of GFP. The vari-ous GFP fusion proteins were purified from Es-cherichia coli and characterized for their ability to enter mammalian cells using Western blot analysis, confocal microscopy and flow cytometry. The GFP fusion protein with Tat PTD at its C-terminus was taken up as efficiently as the GFP fusion protein with Tat PTD at its N-terminus. However, the same protein with PTDs at its both termini was taken up even more efficiently. All the GFP fusion proteins were present in both the nucleus and cytosol of the transduced cells. Uptake was lower at 4

Keywords: HIV-1-Tat, Protein Therapy, Protein Transduction, Tat-GFP-Tat, Transduction Efficiency