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, Tat(47-57)-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 Tat(47-57)-Oct4 fusion protein was similar to 210 mg/l. Following pilot-scale fermentation, Tat(47-57)-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 Tat(47-57)-Oct4 to cross the cell membrane. The results demonstrated that the experimental procedure developed in the present study could produce large quantities of active Tat(47-57)-Oct4 fusion protein from P. pastoris.