Biotechnological production of acetylated thymosin β4

Thymosin β4 (43 aa) is a highly conserved acidic peptide, which regulates actin polymerization in mammalian cells by sequestering globular actin. Thymosin β4 is undergoing clinical trials as a drug for treatment of venous stasis ulcers, corneal wounds and injuries, as well as acute myocardial infarction. Currently, thymosin β4 is produced by a solid-phase chemical synthesis. Biotechnological synthesis of this peptide is difficult, because the N-terminal amino acid residue of thymosin β4 playing an essential role in the actin interaction is acetylated. In this study, we proposed a method for production of a thymosin β4 recombinant precursor and its directed chemical acetylation. Deacetylthymosin β4 was synthesized as a part of a hybrid protein containing thioredoxin and a specific TEV (tobacco etch virus) protease cleavage site. The following scheme was developed for purification of deacetylthymosin β4: (i) biosynthesis of a soluble hybrid protein (HP) in Escherichia coli, (ii) isolation of HP by ion exchange chromatography, (iii) cleavage of HP with TEV protease, and (iv) purification of deacetylthymosin β4 by ultrafiltration. N-Terminal acetylation of the serine residue of deacetylthymosin β4 was performed with acetic anhydride under acidic conditions (pH 3.0). The reaction yield was 55%. Thymosin β4 was finally purified by reverse-phase HPLC. The proposed method of isolation of recombinant thymosin β4 can be scaled-up and provide a highly purified preparation in a yield of 20 mg per 1 L of culture suitable for use in medical practice.