Investigating the rPF4 secretion through the T1SS and T2SS.

Protein expression and secretion were carried out in 7 mL of LB or TB media for 18 h. Induction was triggered at 0.5 mM IPTG. BL refers to the cleared bacterial lysate. E1/TB and E1/LB indicate the secreted rPF4 proteins in TB or LB media respectively following purification. (A) Represents the T2SS-mediated rPF4 protein secretion into the extracellular milieu using pelB leader peptide. (B) Represents the T1SS-mediated rPF4 protein secretion into the extracellular milieu using HLA signal peptide. As demonstrated in the figures, the T2SS is more efficient in secreting the rPF4 compared to the T1SS. Furthermore, as confirmed by the SDS-PAGE analysis, growth in the TB medium enhances the protein secretion process and is superior to the LB medium.