Transportan

A common characteristic of CPPs is that they contain a minimal motif of less than 20 amino acids rich in basic residues. There are two subclasses of CPPs the first class consists of amphipathic helical peptides, where lysine is the predominant supplier of the positive charge, for example model amphipathic peptide (MAP) and transportan, whereas the second group, which includes TAT and penetratin, is rich in arginine residues (48-60,86). 

Lindberg, M., J. Jarvet, U. Langel, and A. Graslund (2001) Secondary structure and position of the cell-penetrating peptide transportan in SDS micelles as determined by NMR. Biochemistry 40, 3141-3149. 

Barany-Wallje E., A. Andersson, A. Graslund, and L. Maler (2006) Dynamics of transportan in bicelles is surface charge dependent. J. Biomol. NMR 35, 137-147. 

A 27 amino acid chimeric peptide with cell-penetrating properties. See Cell-Penetrating Peptides. See Pooga, M., Hallbrink, M., Zorko, M., and Lan-gel, ti.. Cell penetration by transportan, FASEB J. 12, 67-77,1998 Padiri, K., Saalik, P, Hansen, M. et al.. Cell transduction pathways of transpor-tans, Biooconjugate Chem. 16, 1399-1410, 2005. 

Key Words Cell-penetrating peptide noninvasive cellular delivery penetratin Tat transportan pVEC MAP protein transduction oligonucleotide transport plasmid delivery. 

Comparison of four CPPs— penetratin (5), Tat (6), transportan (12), and model amphipathic peptide (MAP) (13)— revealed that a model peptide cargo was most efficiently delivered into Bowes melanoma cells by MAP and transportan peptides. As judged by energy transfer experiments (31), the intracellular concentration of a cargo peptide delivered into cells by penetratin or Tat remained three- to fourfold lower compared with transportan- and MAP-mediated delivery. On the other hand, transportan and MAP were more noxious to cells and increased the plasma membrane permeability at lower concentrations. Import of penetratin sequences by the melanoma-derived SKMel-37 cells was in turn three- to fourfold more efficient than uptake of MTS-sequences as measured by fluorescence correlation spectroscopy in living cells and by FACS analysis (32). 

Pooga, M., Hallbrink, M., and Langel, U. (2002) Transportans, in Cell Penetrating Peptides, Processes and Applications (Langel, U., ed.), CRC Press, Boca Raton, London, New York, Washington, pp. 53-70. 

An important question is how to achieve the most efficient delivery of PNA. This problem does not usually have a definite answer and many different factors must be considered. Table 1 reviews the main types of PNA-peptide conjugates and indicates the most important issues in each case. The internalization routes are schematically drawn in Fig. 2. Depending on the peptide attached, the PNA oligomer is internalized via endocytosis or directly delivered across the cell membrane. For nuclear localization signals (NLS) and tetralysine (K4) the delivery route is not clear yet. The same holds true for nuclear delivery with CPPs. Some CPPs (e.g., transportan) have been shown to accumulate in the nucleus, while others have not. 

The designer must not forget strategically important sites in the peptide. For example, it is believed that the free N-terminal is important for the internalization of transportan and, therefore, the side-chain of Lys in position 13 is used for cargo attachment (28). It is believed, although not clearly demonstrated... 

Transportan Synthetic (galanin, mastoparan) GWTLNSAGYLLG- KINLKALAALAKKIL Amphipathic Y 121... 

Peptides Derived from Homeodomain Proteins Can Translocate across a Cell Membrane. Homeodomain proteins are transcription factors that are expressed during development and, in some tissues, throughout adult life. These factors, which act by binding to DNA within the nucleus, must translocate across membranes to function. Recent studies suggest that the ability of peptides derived from the third helix of Drosophila Antennapedia homeobox (Antp-HD) to cross membranes is conferred by domains rich in basic amino acids (Table 8.8). A number of other proteins—such as HIV-1 Tat protein [62], transportan [63], and basic amino acid-rich model proteins [64]—have domains that provide a similar enhanced permeation function. 

The mechanism of peptide transport into the cell is still uncertain. Peptides derived from Antp-HD appear to be internalized by a receptor-independent mechanism that depends on direct interaction with membrane lipids peptide association with lipids and internalization via an inverted micelle that crosses the membrane, has been suggested [65]. In the case of transportan (Table 8.8), binding to the cell surface and internalization occur quickly (in 1 min with maximum concentration at 20 min) and efficiently (10-16% uptake) [63]. As in Antp-HD, uptake does not appear to require specific receptors, as internalization is not saturable. Once in the cell, most of the peptide is associated with membranes, including the nuclear membrane. Similar observations have been reported in Tat peptide sequence derived from HIV-1 [62]. 

Pooga M, Hallbrink M, Zorko M, Langel U. Cell penetration by transportan. FASEB J 1998 12 67 77. 

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