Protein transduction domain PTD

Already in 1965, Ryser and Hancock provided evidence that histones and polyamino acids could greatly enhance albumin uptake by cultured tumor cells (6). More recently, several polybasic peptides (so-called protein transduction domains, PTDs or cell-penetrating peptides, CPPs) have been shown to efficiently mediate uptake of nucleic acids, bioactive peptides, phage particles, and liposomes into a wide variety of mammalian cells. The initially proposed ability of CPPs to penetrate plasma membranes via a temperature-independent, non-endocytotic pathway was later shown to be a fixation artifact, and it is currently widely accepted that CPP-mediated macromolecular delivery follows energy-dependent endocytotic pathways that in most cases depend on the expression of cell-surface heparan sulfate proteoglycans (HSPGs) (7). 

Fig. 10.1-12 Principle of protein semisynthesis in living cells. The protein transduction domain (PTD) delivers the probe to the cell, which is followed by complementation of the DnaE intein halves and protein splicing.

Over the past decade, the unique activity of oligopeptides, known as protein transduction domains (PTDs) or cell penetrating peptides (CPPs), has made it possible to transduce biologically active macromolecules into living cells [2, 3]. It was accomplished by conjugating a PTD to the desired macromolecule. Various kinds of macromolecules have been successfully internalized into living... 

Bogoyevitch M A, Kendrick T S, Ng D C H and Barr R K, Taking the cell by stealth or storm Protein Transduction Domains (PTDs) as versatile vectors for delivery , DNA Cell Biol, 2002 21 (12) 879-894. 

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