Identification of Toxoplasma gondii proteins binding human lactoferrin: a new aspect of rhoptry proteins function.

In this paper, we report on the isolation, purification and identification of two Toxoplasma gondii membrane proteins binding human lactoferrin. Parasite membrane proteins were isolated using the commercial Mem-PER Eukaryotic Membrane Protein Extraction System. After purification by lactoferrin affinity chromatography, three protein bands were detected with the molecular mass of 74, 63 and 58 kDa, two of which (63 and 58 kDa) specifically bound biotin labeled human lactoferrin as examined by competitive inhibition. Further identification of latter proteins by ESI/MS/MS amino acid sequencing technique revealed those proteins as Toxoplasma ROP4 (band 63 kDa) and ROP2 (band 58 kDa) antigens known to be involved in many mechanisms essential for the parasite pathogenicity, including host lactoferrin acquisition as determined in this study.