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Structures of the Toxoplasma gliding motility adhesin.


ABSTRACT: Micronemal 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 ?-C-linked to Trp-276 in TSR1 has an unusual (1)C4 chair conformation. The MIC2 VWA domain includes a mobile ?5-helix and a 22-residue disordered region containing two disulfide bonds in place of an ?6-helix. A hydrophobic residue in the prodomain binds to a pocket adjacent to the ?7-helix that pistons in opening of the VWA domain to a putative high-affinity state.

SUBMITTER: Song G 

PROVIDER: S-EPMC3977308 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature

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Structures of the Toxoplasma gliding motility adhesin.

Song Gaojie G   Springer Timothy A TA  

Proceedings of the National Academy of Sciences of the United States of America 20140317 13


Micronemal 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 elon  ...[more]

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