Abstract
Immediately prior to invasion Toxoplasma gondii tachyzoites release a large number of micronemal proteins (TgMICs) that participate in host cell attachment and penetration. The TgMIC4-MIC1-MIC6 complex was the first to be identified in T. gondii and has been recently shown to be critical in invasion. This study establishes that the N-terminal thrombospondin type I repeat-like domains (TSR1-like) from TgMIC1 function as an independent adhesin as well as promoting association with TgMIC4. Using the newly solved three-dimensional structure of the C-terminal domain of TgMIC1 we have identified a novel Galectin-like fold that does not possess carbohydrate binding properties and redefines the architecture of TgMIC1. Instead, the TgMIC1 Galectin-like domain interacts and stabilizes TgMIC6, which provides the basis for a highly specific quality control mechanism for successful exit from the early secretory compartments and for subsequent trafficking of the complex to the micronemes.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Blotting, Western
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Carbohydrates / chemistry
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Cell Adhesion
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Cell Adhesion Molecules / chemistry*
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Cell Adhesion Molecules / metabolism
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Cell Adhesion Molecules / physiology
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Cloning, Molecular
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Endoplasmic Reticulum / metabolism
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Escherichia coli / metabolism
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Fluorescent Antibody Technique, Indirect
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Galectins / chemistry*
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Golgi Apparatus / metabolism
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Humans
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Immunoprecipitation
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Magnetic Resonance Spectroscopy
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Microscopy, Confocal
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Microscopy, Fluorescence
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Models, Biological
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Molecular Conformation
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Neoplasm Invasiveness
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Pichia / metabolism
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Protein Binding
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Protein Conformation
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Protein Folding
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Protein Structure, Secondary
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Protein Structure, Tertiary
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Protein Transport
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Protozoan Proteins / chemistry*
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Protozoan Proteins / metabolism
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Protozoan Proteins / physiology
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Thrombospondins / metabolism
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Toxoplasma / metabolism*
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Transfection
Substances
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Carbohydrates
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Cell Adhesion Molecules
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Galectins
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MIC1 protein, Toxoplasma gondii
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MIC4 protein, Toxoplasma gondii
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Protozoan Proteins
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Thrombospondins