The Interaction Between Plasma Lipoprotein(a) And Recombinant Elongation Factor Tu Derived From Pseudomonas Aeruginosa

Pseudomonas aeruginosa (P. aeruginosa) recruits human plasminogen (Pig) via the surface protein enlongation factor Tu (Tu). P. aeruginosa-bound Pig is converted by plasminogen activators to proteolytically active plasmin that degrades extracellular matrix (ECM) and may enhance tissue evasion of the baterium.Plasma lipoprotein(a) [Lp(a)] contains a LDL-like domain and an apolipoprotein(a) [apo(a)] sharing a high homology with Pig. We have previously hypothesized that Lp(a) might compete with Pig for the binding to pathogens and might be a potent anti-infective molecule in vivo. Here, it was tested whether Lp(a) inhibited P. aeruginosa from recruiting of Pig using his-tagged recombinant protein Tu (rTu), live P. aeruginosa and the polyclonal mouse anti-rTu IgG.Tu was recombinantly expressed in E. coli and purified by affinity chromatography. Immobilized rTu bound to Pig or Lp(a) specifically but not to LDL, indicating that apo(a) is relevant for the binding of rTu. Lysine-binding sites (LBS) are responsible for the interaction as the lysine analog ε-aminocaproic acid (EACA) inhibited the binding of Pig or Lp(a) to rTu. Lp(a) dramatically inhibited the interaction between Pig and Tu, suggesting that Lp(a) and Plg use similar or even overlapping binding sites.Whole cell Enzyme-linked immunosorbent assay (ELISA) demonstrated that intact P. aeruginosa attaches Pig, Lp(a) and LDL. LBS are responsible for the attachment to Pig or Lp(a) since EACA inhibited the interaction of Plg or Lp(a) with the bacterium. The expressing levels of surface-exposed Tu at different growth phases of P. aeruginosa varied significantly detected by mouse anti-rTu IgG. However, there was no binding difference of Pig or Lp(a) to P. aeruginosa at stationary phase or exponential phase, implying that the microbe utilized other surface proteins for the binding.