Protransducine-c: gene transfer activator

A polypeptide having a sequence similarity of at least 80% with the sequence

• wherein
• Z1 or Z3 have the same meaning or independently represent the N-terminal end of the polypeptide, or independently are the amino acids Leu or Ser or the following peptides
• Ser-Asn, Ser-Asn-Asn, Ser-Asn-Asn-Ile, Ser-Asn-Asn-Ile-Thr, Thr-Leu, Ile-Thr-Leu, Asn-Ile-Thr-Leu, Asn-Asn-Ile-Thr-Leu, or Ser-Asn-Asn-Ile-Thr-Leu,
• Z2 or Z4 have the same meaning or independently represent the C-terminal end of the polypeptide, or independently are the amino acids Gly or Glu or the following peptides
• Glu-Val, Glu-Val-Gly, Glu-Val-Gly-Lys, Glu-Val-Gly-Lys-Ala, Glu-Val-Gly-Lys-Ala-Met, Glu-Val-Gly-Lys-Ala-Met-Tyr, Glu-Val-Gly-Lys-Ala-Met-Tyr-Ala, Glu-Val-Gly-Lys-Ala-Met-Tyr-Ala-Pro, Glu-Val-Gly-Lys-Ala-Met-Tyr-Ala-Pro-Pro, Glu-Val-Gly-Lys-Ala-Met-Tyr-Ala-Pro-Pro-Ile, Glu-Val-Gly-Lys-Ala-Met-Tyr-Ala-Pro-Pro-Ile-Glu, Glu-Val-Gly-Lys-Ala-Met-Tyr-Ala-Pro-Pro-Ile-Glu-Gly, Glu-Gly, Ile-Glu-Gly, Pro-Re-Glu-Gly, Pro-Pro-Ile-Glu-Gly, Ala-Pro-Pro-Ile-Glu-Gly, Tyr-Ala-Pro-Pro-Ile-Glu-Gly, Met-Tyr-Ala-Pro-Pro-Ile-Glu-Gly, Ala-Met-Tyr-Ala-Pro-Pro-Ile-Glu-Gly, Lys-Ala-Met-Tyr-Ala-Pro-Pro-Ile-Glu-Gly, Gly-Lys-Ala-Met-Tyr-Ala-Pro-Pro-Ile-Glu-Gly, Val-Gly-Lys-Ala-Met-Tyr-Ala-Pro-Pro-Ile-Glu-Gly, or Glu-Val-Gly-Lys-Ala-Met-Tyr-Ala-Pro-Pro-Ile-Glu-Gly.