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  • 标题:Structures of the Toxoplasma gliding motility adhesin
  • 本地全文:下载
  • 作者:Gaojie Song ; Timothy A. Springer
  • 期刊名称:Proceedings of the National Academy of Sciences
  • 印刷版ISSN:0027-8424
  • 电子版ISSN:1091-6490
  • 出版年度:2014
  • 卷号:111
  • 期号:13
  • 页码:4862-4867
  • DOI:10.1073/pnas.1403059111
  • 语种:English
  • 出版社:The National Academy of Sciences of the United States of America
  • 摘要: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 1C4 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.
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