Fig. 3.

Design of the fusion proteins and genome editing for the display system. a Structure of OmpF and the amino acid sequences of the epitope inserts (red). Epitope peptide was designed to be integrated into OmpF loop 8 for surface display. b Genome editing for insertion of the epitopes into OmpF in E. coli. The protospacer for CRISPR system target is shaded in blue in OmpF. DNA sequencing was used to verify the editing of the bacterial genome. The translated amino acid sequences are consistent with the epitope sequences (E6F6, TSTGPCKTCTTPA; 14H6, QLYKTCKQAGTCPPDII). c Genetic sequences and corresponding amino acid sequences of epitope inserts in constructed plasmids pF-HB, pF-L2, pC-HB, and pC-L2. The original and epitope-grafted sequences of OmpF from the ER2566 strain and OmpC from the K12 strain are shown. Black arrows indicate the sites of epitope insertion