The present invention concerns a polypeptide comprising the sequence X1WX2X3X4RX5X6X7 X8 X9, and derivatives thereof, wherein X1 is an amino acid selected in the group consisting in histidinc (H), tyrosinc (Y), aspartic acid (D), glutamine (Q), and leucine (L), preferably histidine (H) or tyrosine (Y); X2 is a polar amino acid, charged or not, and selected in the group consisting in serine (S) threonine (T), lysine (K), arginine (R), asparagine (N), aspartic acid (D), cysteine (C), glycine (G), glutamine (Q), histidine (H), and glutamic acid (E); X3 is a polar amino acid, charged or not, and selected in the group consisting in serine (S), threonine (T), asparagine (N), cysteine (C), histidine (H), leucine (L), tyrosine (Y), alanine (A), and isoleucine (1); X4 is an amino acid selected in the group consisting in threonine (T), arginine (R), asparagine (N), alanine (A), isoleucine (I), leucine (L), methionine (M), phenylalanine (F), tryptophane (W), valine (V) and tyrosine; X5 is an amino acid selected in the group consisting in leucine (L), methionine (M), isoleucine (I), tryptophane (W), tyrosine (Y), histidine (H), glutamine (Q), lysine (K), and arginine (R); X6 is an amino acid selected in the group consisting in leucine (L), and glutamic acid (E); X7 is an amino acid selected in the group consisting in cysteine (C), asparagine (N), alanine (A), tyrosine (Y), serine (S), glutamine (Q), and proline (P); X8 is a hydrophobic amino acid selected in the group consisting in alanine (A), isoleucine (I), leucine (L), methionine (M), phenylalanine (F), tryptophane (W), valine (V) and tyrosine; and X9 is a threonine or an hydrophobic amino acid selected in the group consisting in alanine (A), isoleucine (I), leucine (L), methionine (M), phenylalanine (F), tryptophane (W), valine (V) and tyrosine.