Site selective acylation

Polypeptide consisting of a four helix bundle formed of two dimerized helix-loop-helix motifs, one of said helix-loop-helix motifs having a sequence according to SEQ. ID. No. 6, and the other of said helix-loop-helix motifs having a sequence according to SEQ. ID. No. 1, SEQ. ID. No. 2, SEQ. ID. No.3, SEQ. ID. No.4, SEQ. ID. No. 5 or SEQ. ID. No. 7.

A method for site-selective acylation of a folded polypeptide and/or protein based on the use of a chemical structure element consisting of a four helix bundle formed of two dimerized helix-loop-helix motifs folded in an antiparallel mode, said helix-loop-helix motifs comprising amino acid residues in a heptad repeat pattern (a b c d e f g)n, wherein all but 1-3 of said amino acid residues in positions a and d are non-polar and wherein said 1-3 amino acid residues in positions a and d that are polar independently are selected from the group consisting of lysine, ornithine, diaminobutyric acid and homolysine, wherein said amino acid residues in positions a and d form a hydrophobic core, wherein the polypeptide and/or protein to be acylated is placed in an aqueous solution, followed by the sequential addition of 1-3 acylation agents, if such acylating agents are not already present in the solution, resulting in acylation of said 1-3 polar amino acid residues in positions a and d.