Proteomic characterization of the pellicle of Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular parasite. The ability to invade cells and proliferate successfully is given by the machinery found in the pellicle of the parasite, the pellicle is a complex of three membranes. Despite the importance of the pellicle in the biology of Toxoplasma, its protein composition had not been reported. The proteins of the isolated pellicle fraction were digested with trypsin and chymotrypsin, for their identification and quantification in the case of those digested with trypsin and only identification in the case of those digested with chymotrypsin. Samples were resolved, and peptides were separated using a UHPLC ACQUITY M-Class. Spectral data were acquired in an MS with electrospray ionization and ion mobility separation Synapt G2-Si operated with data-independent acquisition and ion mobility spectrometry using the high-definition multiplexed MS/MS mode. We used the Hi3 method to quantify absolutely every protein detected. In the isolate of pellicle digested with trypsin a total of 548 proteins were identified and absolutely quantified using the internal standard and the intensity of the most abundant peptides per protein with Progenesis QI software and the database UP000002494. Among identified proteins, 11 corresponded to IMC, 11 were related to SAG (SRS), 15 to plasma membrane and glideosome and 13 to cytoskeleton (CK). In the chymotrypsin-digested pellicle sample a total of 137 proteins were identified and 22 of them were proteins that were not identified in the trypsin-digested sample. Due to the characteristics of the SRS proteins, they have a role in generating the host's immune response or are involved in adhesion, motility and invasion. The 11 proteins found with the analysis of E. mass. Study of these SRS proteins to determine their role in the dynamic events of the parasite, such as adhesion and motility as well as in the generation of the immune response, is important in the search for therapies against toxoplasmosis