Figure 1

(a) Expression level and enzyme activity of secreted SrtA mediated by signal peptides in E. coli; 1: FdnG, 2: OmpA, 3: TorA, 4: PelB, 5: DmsA, and 6: control (without signal peptide). (b) SDS-PAGE of culture supernatant from E. coli BL21 (DE3) encoding signal peptides; lane M: protein marker, lanes 1–6: FdnG, OmpA, TorA, PelB, DmsA, and control (without signal peptide). (c) Expression level and enzymatic activity of secreted SrtA including the PelB signal peptide with codon optimization and molecular chaperone co-expression in E. coli; 1: GroES/GroEL, 2: Tig, 3: GroES/GroEL/DnaK/DnaJ/GrpE, 4: DnaK/DnaJ/GrpE, 5: GroES/GroEL/Tig, 6: control (without codon optimization and molecular chaperones), and 7: codon optimization only. (d) SDS-PAGE of culture supernatant from E. coli BL21 (DE3) encoding signal peptides with or without codon optimization and molecular chaperone co-expression; lane M: protein marker, lane P: purified SrtA, lane 1–7: GroES/GroEL, Tig, GroES/GroEL/DnaK/DnaJ/GrpE, DnaK/DnaJ/GrpE, GroES/GroEL/Tig, control (without codon optimization and molecular chaperones), and codon optimization only. All of the experiments were performed in triplicate, and the data are the mean values with the standard deviation.