FIGURE 1.

The strategy of the cell surface display system. (A) A randomized peptide library is constructed based on preS1 aa2-21. The fusion protein contains a mCherry, a FasL transmembrane domain, a preS1 aa2-21, and a 7-aa randomized peptide. (B) A cell library displaying the fusion proteins was created using the Sleeping Beauty transposon system. (C) The cell library was incubated with cell membrane segments carrying NTCP-GFP, and those cells expressing high-affinity peptides would bind more NTCP-GFP. (D) Red fluorescent (mCherry) cells with relatively higher green fluorescence (GFP) were sorted by flow cytometry. (E) The selected cells were amplified before moving on to the next round of the screening process. (F) Genomic DNA was extracted from the final enriched cells. Fragments containing target sequences were amplified by PCR and sequenced to identify the enriched peptides.