Acyl Transfer Proteins

Acyl-transporting proteins are relatively small (about 80 amino acid residues) negatively charged molecules folded in alpha-helix and similar in different groups of organisms in amino acid sequence. The structure of many acyl transfer proteins has been described using nuclear magnetic resonance and crystallography methods.

The protein is expressed in the form of apoprotein (inactive form). Holoprotein (active form) is formed as a result of the transfer of the phosphopanthetein residue from coenzyme A to the conserved serine residue in the middle of the peptide chain. The reaction is carried out by 4′-phosphopantethein transferase - synthase of holo-acyl transfer proteins.

4′-Phosphopantethein is a necessary prosthetic group of a number of acyl-carrying proteins involved in primary and secondary metabolism, including acyl-carrying proteins of fatty acid synthases and polyketides synthases (as well as peptidyl-carrying and aryl-carrying proteins of synthetase of non-ribosomal peptides ). The substrate is bound via an energy-rich thioether bond (with the thioethanolamine residue in phosphopanthetein).

The large length and flexible structure of the prosthetic group allows the substrate associated with it to reach various active sites within multi-enzyme complexes (for example, type I fatty acid synthase), which increases the effective concentration of the substrate concentration and allows the synthesis process to be carried out in the “assembly line” mode.

Acyl transfer proteins are similar in structure and mechanism of work with peptidyl transfer proteins of synthetases of nonribosomal peptides .

• Chan DI, Vogel HJ Current understanding of fatty acid biosynthesis and the acyl carrier protein // Biochemical Journal. - 2010 .-- Vol. 430. - P. 1-19. - DOI : 10.1042 / BJ20100462 .