Construction and in vitro activity evaluation of protein transduction domain-transactivator of transcription and <i>Candida antarctica</i> lipase B fusion proteins

Protein transduction domain (PTD)- transactivator of transcription (Tat) and the alkaline cold-active lipase Candida antarctica lipase B (calB) were used to construct a calB-Tat recombinant protein and examine its membrane-penetrating ability. The calB gene was fused with a PTD-Tat-encoding fragment to create the in-frame calB-Tat. After digestion with Nco I and Xho I, the calB-Tat fragment was subcloned and inserted into the expression vector pET28a. The recombinant plasmid pET28a-calB-Tat was subsequently transferred into <i>E.coli</i> Rosetta (DE3) cells to express the labeled protein calB-Tat. Protein concentrations were measured using a commercial BCA kit, and the transmembrane activity of the proteins in SH-SY5Y cells was observed under a fluorescence-inverted microscope. MTT and Western blotting assays were conducted to examine toxicity. The fusion protein exhibited low toxicity. As the concentration of the fusion protein decreased, the effect on cell viability decreased. Additionally, the fusion protein penetrated the cell membrane penetration was stable and was specifically expressed in cells. Taken together, the pET28a-calB-Tat prokaryotic vector was generated, yielding a significant amount of the calB-Tat protein. This increased the cell membrane and perhaps reveals a new way of delivering weight-loss drugs and protein-based medications.