Background: Insulin is a peptide hormone used for regulating blood glucose levels.
Human insulin market is projected to grow at a rate of 12.5% annually. To meet the needs of
patients, a cost effective insulin manufacturing strategy has to be developed. This can be achieved
by selecting a competent host, ideal fusion tag and streamlined downstream process.
Objective: In this article, we have demonstrated that selecting a right fusion partner for expression
of toxic proteins like insulin, plays a major role in increasing the recombinant protein yield.
Methods: In this article, we have focused on identifying a peptide tag fusion partner for expressing
proinsulin by truncating thioredoxin tag. Truncations were carried out from both Amino and
Carboxy terminus of the protein and efficiency of truncated sequences was evaluated by expressing
it with proinsulin gene. FCTRX (1-15) sequence fused to proinsulin was processed further to
establish downstream protocol for purification.
Results: Thioredoxin tag was truncated appropriately by considering the fusion tag: protein ratio. A
couple of sequences ranging 10 – 15 amino acids were identified based on its in silico properties.
Of these FCTRX (1-15) showed increased expression and stability of fusion protein. 156 mg of
purified insulin was generated from 1g of inclusion body after enzymatic conversion and
Conclusion: As a result of the current study, it was concluded that FCTRX (1-15) peptide has
advantageous attributes to be considered as an ideal fusion tag for expression of proinsulin. This
can be further explored by expressing it with other proteins.