| Summary: | Microneme proteins (MICs) belong to a protein family that is actively involved in the invasion of host cells by apicomplexan parasites. Among these proteins, MIC2 is a member of the Thrombospondin-related anonymous (TRAP) family of adhesive proteins, which are highly conserved within the apicomplexans. The other microneme protein M2AP, known to facilitate the transport of MIC2 through the secretory network, is also essential to the virulence of the parasite. Most importantly, MIC2 and M2AP form a multimeric functional complex that presents in the cell invasive stages and serves as the prototype of other TRAP family members. This thesis describes the NMR assignments and two solution structure calculations of M2AP and a Thrombospondin type-1 repeats (TSR-1) domain. M2AP is composed exclusively of beta strands and, despite no sequence similarity, demonstrates clear structural similarity to the galectin-like domain from MIC1. And TSR-1 repeats from MIC2 demonstrate two typical TSR-like-fold domains. Interactional studies reveal that the M2AP binds both the first and the last pair of TSR-1 repeats of MIC2. The results on structure–function relationship of MIC2 and M2AP reinforce the critical role of TRAP protein in the successful invasion of cells by T. gondii and reveal potential therapeutic targets that may be used to control toxoplasmosis.
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