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.