Nucleic Acids Res  2003 Jan 15;31(2):556-61 

Cellular uptake of Antennapedia Penetratin peptides is a two-step process in
which phase transfer precedes a tryptophan-dependent translocation.

Dom G, Shaw-Jackson C, Matis C, Bouffioux O, Picard JJ, Prochiantz A,
Mingeot-Leclercq MP, Brasseur R, Rezsohazy R.

Unit of Developmental Genetics, Universite Catholique de Louvain, 73 (boite 82)
avenue Mounier, 1200 Brussels, Belgium.

Several homeodomains and homeodomain-containing proteins enter live cells
through a receptor- and energy-independent mechanism. Translocation through
biological membranes is conferred by the third alpha-helix of the homeodomain,
also known as Penetratin. Biophysical studies demonstrate that entry of
Penetratin into cells requires its binding to surface lipids but that binding
and translocation are differentially affected by modifications of some
physico-chemical properties of the peptide, like helical amphipathicity or net
charge. This suggests that the plasma membrane lipid composition affects the
internalization of Penetratin and that internalization requires both lipid
binding and other specific properties. Using a phase transfer assay, it is shown
that negatively charged lipids promote the transfer of Penetratin from a
hydrophilic into a hydrophobic environment, probably through charge
neutralization. Accordingly, transfer into a hydrophobic milieu can also be
obtained in the absence of negatively charged lipids, by the addition of DNA
oligonucleotides. Strikingly, phase transfer by charge neutralization was also
observed with a variant peptide of same charge and hydrophobicity in which the
tryptophan at position 6 was replaced by a phenylalanine. However, Penetratin,
but not its mutant version, is internalized by live cells. This underscores that
charge neutralization and phase transfer represent only a first step in the
internalization process and that further crossing of a biological membrane
necessitates the critical tryptophan residue at position 6.

PMID: 12527762 [PubMed - in process]