Getting hydrophilic compounds into cells: lessons from homeopeptides.

The homeodomain of Antennapedia, a Drosophila transcription factor, translocates across biological membranes. Within this 60-amino-acid polypeptide, a shorter sequence of 16 amino acids was identified that can be used as an internalization vector for several types of cargo (i.e. other peptides and oligonucleotides) into the cytoplasm and nucleus of all cell types. This article describes our present understanding of this phenomenon and discusses its potential applications in cell biology.