Structural highlights
FunctionPublication Abstract from PubMedMicronemal protein 2 (MIC2) is the key adhesin that supports gliding motility and host cell invasion by Toxoplasma gondii. With a von Willebrand factor A (VWA) domain and six thrombospondin repeat domains (TSR1-6) in its ectodomain, MIC2 connects to the parasite actomyosin system through its cytoplasmic tail. MIC2-associated protein (M2AP) binds noncovalently to the MIC2 ectodomain. MIC2 and M2AP are stored in micronemes as proforms. We find that the MIC2-M2AP ectodomain complex is a highly elongated 1:1 monomer with M2AP bound to the TSR6 domain. Crystal structures of N-terminal fragments containing the VWA and TSR1 domains for proMIC2 and MIC2 reveal a closed conformation of the VWA domain and how it associates with the TSR1 domain. A long, proline-rich, disulfide-bonded pigtail loop in TSR1 overlaps the VWA domain. Mannose alpha-C-linked to Trp-276 in TSR1 has an unusual (1)C4 chair conformation. The MIC2 VWA domain includes a mobile alpha5-helix and a 22-residue disordered region containing two disulfide bonds in place of an alpha6-helix. A hydrophobic residue in the prodomain binds to a pocket adjacent to the alpha7-helix that pistons in opening of the VWA domain to a putative high-affinity state. Structures of the Toxoplasma gliding motility adhesin.,Song G, Springer TA Proc Natl Acad Sci U S A. 2014 Apr 1;111(13):4862-7. doi:, 10.1073/pnas.1403059111. Epub 2014 Mar 17. PMID:24639528[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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