Expression, purification and characterization of a recombinant Tat47–57-Oct4 fusion protein in Pichia pastoris

The transcription factor, Oct-4, is involved in the self-renewal of undifferentiated embryonic stem cells, and is also significant in the reprogramming process and in the development of tumors. In the present study, the fusion protein, Tat47‑57-Oct4, was secreted by the signal peptide of human serum albumin in Pichia pastoris under the control of alcohol oxidase promoter 1. The yield of recombinant Tat47‑57-Oct4 fusion protein was ~210 mg/l. Following pilot‑scale fermentation, Tat47‑57-Oct4 was purified by ammonium sulfate precipitation, Vivaflow 200 ultrafiltration and SP Sepharose fast flow chromatography in order to obtain 95.6% purity. Immunofluorescence analysis validated the ability of Tat47‑57-Oct4 to cross the cell membrane. The results demonstrated that the experimental procedure developed in the present study could produce large quantities of active Tat47‑57-Oct4 fusion protein from P. pastoris.