Antennapedia Peptide, acid

The Antennapedia homeodomain protein of Drosophila has the ability to penetrate biological membranes and the third helix of this protein, residues 43-58, known as penetratin (RQIKIWFQNRRMKWKK-amide) has the same translocating properties as the entire protein.
This is a 16 amino acid peptide corresponding to the region within the Drosophila Antennapedia DNA binding domain that is mapped to be responsible for cellular internalization. The peptide has been shown to be able to translocate through the plasma membrane to the cytosol and nucleus of living cells, both at 37 °C and 4 °C.