The Interaction Between Lipoprotein(a) And Recombinant Protein E Derived From Nontypeable Haemophilus Influenzae

Protein E(PE),with two lysine residues at its C-terminus,is a plasminogen(Plg)receptor on the surface of nontypeable Haemophilus influenza(NTHi).NTHi can recruit Plg on the cell surface by PE and utilize host fibrinolytic system to achieve its immune invasion.Based on the high homology of Plg and Apolipoprotein(a)[Apo(a)] of Lipoprotein(a)[Lp(a)],Lp(a)was supposed to bind to PE.In this study,the recombinant PE(rPE)and C-terminal lysine residues-deleted variant(rPE?KK)were obtained by prokaryotic expression and further purified.Lp(a)was isolated and purified from human plasma by KBr density gradient centrifugation followed by Q Sepharose? Fast Flow ion exchange chromatography.The interaction between rPE,rPE?KK and Lp(a)was investigated by enzyme-linked immunosorbent assay(ELISA)and Pull down followed by Western blot.The results indicated that rPE could bind to Lp(a)but not to LDL,and the interaction was significantly inhibited by EACA.The binding capacity of rPE?KK to Lp(a)was obviously lower than that of rPE.In addition,Lp(a)could inhibit the binding of rPE to Plg slightly.In overall,Lp(a)could bind to rPE and the C-terminal lysine residues of rPE and the lysine binding site(LBS)of Apo(a)was responsible for this interaction.To our knowledge,it is first time to report the interaction between rPE and Lp(a),which provides a new clue to further study of the physiological role of Lp(a).