Production and characterization of highly purified recombinant thymosin beta 4 in Escherichia coli.

Thymosin β4 (Tβ4) is a small peptide composed of 43 amino acids. It has many important biological functions, such as promoting cardiac repair and wound healing, and therefore has great potential in clinical applications. In this report, we describe a novel and efficient way to produce highly purified and active Tβ4. It was expressed in a soluble form using a DsbA and hexahistindine tag in Escherichia coli (E. coli). Using high cell density cultivation, the final biomass concentration was about 50 g L(-1) dry cell weight with the expression level of the fusion protein being 40%. To obtain highly purified protein, a purification process involving a five-step column procedure was implemented. The purity of Tβ4 was above 98% and all the host cell related impurities, such as endotoxin, host cell protein and residual DNA levels, were within the permissible range listed in the Chinese Pharmacopoeia. The E-rosette test demonstrated that the bioactivity of purified Tβ4 was consistent with other published work. This is the first report producing highly purified Tβ4 from genetically engineered sources.