title: Structural basis of Toxoplasma gondii MIC2-associated protein interaction with MIC2.
abstract: Toxoplasma gondii parasites must actively invade host cells to propagate. Secretory microneme proteins have been shown to be important for both gliding motility and active invasion. MIC2-M2AP is a protein complex that is essential for productive motility and rapid invasion by binding to host cell surface receptors. To investigate the architecture of the MIC2 and M2AP complex, we identified the minimal domains sufficient for interaction and solved the NMR solution structure of the globular domain of M2AP. We found that M2AP adopts a modified galectin fold similar to the C-terminal domain of another microneme protein, MIC1. NMR and immunoprecipitation analyses implicated hydrophobic residues on one face of the M2AP galectin fold in binding to the membrane proximal sixth thrombospondin type I repeat domain of MIC2. Our findings provide a second example of a galectin fold adapted for microneme protein-protein interactions and suggest a conserved strategy for the assembly and folding of diverse protein complexes.
authors.affiliation: From the Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109 and.
authors.forename: My-Hang
authors.initials: MH
authors.lastname: Huynh
authors.affiliation: the Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
authors.forename: Bing
authors.initials: B
authors.lastname: Liu
authors.affiliation: the Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
authors.forename: Maud
authors.initials: M
authors.lastname: Henry
authors.affiliation: the Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
authors.forename: Lloyd
authors.initials: L
authors.lastname: Liew
authors.affiliation: the Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom s.j.matthews@imperial.ac.uk.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Matthews
authors.affiliation: From the Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109 and vcarruth@umich.edu.
authors.forename: Vern B
authors.initials: VB
authors.lastname: Carruthers
mesh_terms: D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002241:Carbohydrates / Q000737:chemistry; D006224:Cricetinae; D003412:Cricetulus; D005347:Fibroblasts / Q000469:parasitology; D037161:Galectins / Q000737:chemistry; D017353:Gene Deletion; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins / Q000737:chemistry*; D046912:Multiprotein Complexes / Q000737:chemistry; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry*; D019699:Thrombospondins / Q000737:chemistry; D014122:Toxoplasma / Q000737:chemistry*
chemical_list: D002241:Carbohydrates; D037161:Galectins; D008024:Ligands; C408878:MIC2 protein, Toxoplasma gondii; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D015800:Protozoan Proteins; C450759:TgM2AP protein, Toxoplasma gondii; D019699:Thrombospondins
keywords: Cell Invasion; Galectin; M2AP; MIC2; Microneme; Nuclear Magnetic Resonance (NMR); Protein Complex; Toxoplasma gondii