Identification of Plasmodium knowlesi Merozoite Surface Protein-119 (PkMSP-119) novel binding peptides from a phage display library

OBJECTIVE Plasmodium knowlesi, the fifth human malaria parasite, has caused mortality in humans. We aimed to identify P. knowlesi novel binding peptides through a random linear dodecapeptide phage display targeting the 19-kDa fragment of Merozoite Surface Protein-1 protein. METHODS rPkMSP-1(19) protein was heterologously expressed using Expresso (R) Solubility and Expression Screening System and competent E. clone (R) 10G cells according to protocol. Three rounds of biopanning were performed on purified rPkMSP-1(19) to identify binding peptides towards rPkMSP-1(19) using Ph.D.(TM)-12 random phage display library. Binding sites of the identified peptides to PkMSP-1(19) were in silico predicted using the CABS-dock web server. RESULTS Four phage peptide variants that bound to PkMSP-1(19) were identified after three rounds of biopanning, namely Pkd1, Pkd2, Pkd3 and Pkd4. The sequences of both Pkd1 and Pkd2 consist of a large number of histidine residues. Pkdl showed positive binding signal with 6.1 x vs. BSA control. Docking results showed that Pkd1 and Pkd2 were ideal binding peptides for PkMSP-1(19). CONCLUSION We identified two novel binding peptides of PkMSP-1(19), Pkd1 (HFPFHHHKLRAH) and Pkd2 (HPMHMLHKRQHG), through phage display. They provide a valuable starting point for the development of novel therapeutics.