The directly introduction of protein into cells is a critical step in studying of protein function.  Unlike DNA transfection in which the transcriptionally active DNA / Gene is introduced into living cells where protein is made by cellular machinery, protein delivery do not introduce any exogenous DNA and is independents of cell transcription and translation machinery. Therefore, it avoids the potential risk of insertional mutagenesis in host genome and the delivered protein function immediately once gets into the cells.

Several methods for protein delivery have been development, such as Electroporation, Microinjection, protein fusion and traditional cationic lipid carriers. Among those methods, the protein fusion delivery is no doubt the easiest method with non-cytotoxic and being applicable for large scale applications, therefore presents a more attractive approach from therapeutic point of view.

Protein fusion delivery is dependent upon a protein transduction domain (PTD) that fusioned with the target. PTDs are short cationic peptides that can efficiently cross the plasma membrane. A basic form is use multiple Arginines (7 ~15 poly R) as the PTD. The mechanisms about how PTD gain entry into cells is incomplete.

The native PTDs were found in many viral proteins demonstrated the trans-membrane property, such as TAT protein from HIV-1, influenza virus hemagglutinin protein (HA2), the herpes simplex virus 1 (HSV-1) DNA-binding protein VP22 and Drosophila Antennapedia (Antp) homeotic transcription factor.

From phage screening and point mutation screening results, Gentarget developed a preparatory, high efficient protein delivery system utilizes an engineered PTD (InTag^TM).  Target proteins fusioned with this high efficiency PTD, are efficiently delivered into a variety of living cells. It consists of 37 amino acids and shows none or minimal effects on its target's function. Dependent upon the cell types, it demonstrates greater than 10 to 40 folds higher efficiency than ploy-Arginine fusion tag.

The advantages of using Gentarget's InTag^TM protein delivery method are:

• High efficiency protein delivery (so that much less protein is required for your functional assays);
• Able to deliver large protein (>1000 amino acids);
• Cell type independent (good for different mammalian cell culture);
• Rapid delivery and readily acquire protein function (<5min);
• Non-invasive delivery (simply added into cell culture);
• Concentration dependent for a controlled delivery;
• Reversible delivery of protein function;
• Targeting delivery when fusioned with a targeting protein;

Gentarget's InTag^TM protein delivery domain was incorporated into our Eco PCR cloning products (Cat#:  to be launched) for E Coli or mammalian expression of your  transfecion ready proteins. After purification, the expression proteins can simply apply to mammalian cell culture for functional assay in living cells. Gentarget also provides many purified, transfection-ready proteins (see product links).

References

• Yohei MUKAI, Biol. Pharm Bull, 29(8):1570-1574, 2006;
• Panagiotis S. Kabouridis, TRENDS in Biotechnology Vol.21 No.11 November 2003;
• Alan Ho, et al., CANCER RESEARCH 61, 474-477, January 15, 2001;