title: The toxofilin-actin-PP2C complex of Toxoplasma: identification of interacting domains.
abstract: Toxofilin is a 27 kDa protein isolated from the human protozoan parasite Toxoplasma gondii, which causes toxoplasmosis. Toxofilin binds to G-actin, and in vitro studies have shown that it controls elongation of actin filaments by sequestering actin monomers. Toxofilin affinity for G-actin is controlled by the phosphorylation status of its Ser53, which depends on the activities of a casein kinase II and a type 2C serine/threonine phosphatase (PP2C). To get insights into the functional properties of toxofilin, we undertook a structure-function analysis of the protein using a combination of biochemical techniques. We identified a domain that was sufficient to sequester G-actin and that contains three peptide sequences selectively binding to G-actin. Two of these sequences are similar to sequences present in several G- and F-actin-binding proteins, while the third appears to be specific to toxofilin. Additionally, we identified two toxofilin domains that interact with PP2C, one of which contains the Ser53 substrate. In addition to characterizing the interacting domains of toxofilin with its partners, the present study also provides information on an in vivo-based approach to selectively and competitively disrupt the protein-protein interactions that are important to parasite motility.
authors.affiliation: Institut Cochin, Département des Maladies Infectieuses, Paris, F-75014 France.
authors.forename: Gaelle
authors.initials: G
authors.lastname: Jan
authors.forename: Violaine
authors.initials: V
authors.lastname: Delorme
authors.forename: Violaine
authors.initials: V
authors.lastname: David
authors.forename: Celine
authors.initials: C
authors.lastname: Revenu
authors.forename: Angelita
authors.initials: A
authors.lastname: Rebollo
authors.forename: Xavier
authors.initials: X
authors.lastname: Cayla
authors.forename: Isabelle
authors.initials: I
authors.lastname: Tardieux
mesh_terms: D051344:Actin Capping Proteins / Q000737:chemistry / Q000378:metabolism*; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D000071636:Protein Phosphatase 2C; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*; D014122:Toxoplasma / Q000378:metabolism*
chemical_list: D051344:Actin Capping Proteins; D000199:Actins; D046912:Multiprotein Complexes; D015800:Protozoan Proteins; C406004:toxofilin protein, Toxoplasma gondii; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C