title: Tetramerization and cooperativity in Plasmodium falciparum glutathione S-transferase are mediated by atypic loop 113-119.
abstract: Glutathione S-transferase of Plasmodium falciparum (PfGST) displays a peculiar dimer to tetramer transition that causes full enzyme inactivation and loss of its ability to sequester parasitotoxic hemin. Furthermore, binding of hemin is modulated by a cooperative mechanism. Site-directed mutagenesis, steady-state kinetic experiments, and fluorescence anisotropy have been used to verify the possible involvement of loop 113-119 in the tetramerization process and in the cooperative phenomenon. This protein segment is one of the most prominent structural differences between PfGST and other GST isoenzymes. Our results demonstrate that truncation, increased rigidity, or even a simple point mutation of this loop causes a dramatic change in the tetramerization kinetics that becomes at least 100 times slower than in the native enzyme. All of the mutants tested have lost the positive cooperativity for hemin binding, suggesting that the integrity of this peculiar loop is essential for intersubunit communication. Interestingly, the tetramerization process of the native enzyme that occurs rapidly when GSH is removed is prevented not only by GSH but even by oxidized glutathione. This result suggests that protection by PfGST against hemin is independent of the redox status of the parasite cell. Because of the importance of this unique segment in the function/structure of PfGST, it could be a new target for the development of antimalarial drugs.
authors.affiliation: Institute of Animal Physiology, University of Münster, Hindenburgplatz, 55 Münster, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Liebau
authors.affiliation: the Departments of Chemical Sciences and Technologies, 00133 Rome, Italy.
authors.forename: Kutayba F
authors.initials: KF
authors.lastname: Dawood
authors.affiliation: the Departments of Chemical Sciences and Technologies, 00133 Rome, Italy.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Fabrini
authors.affiliation: Institute of Animal Physiology, University of Münster, Hindenburgplatz, 55 Münster, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Fischer-Riepe
authors.affiliation: Institute of Biochemistry, Center for Structural and Cell Biology, University of Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany; Laboratory for Structural Biology of Infection and Inflammation, Deutsches Elektronen Synchrotron, Notkestrasse 85, 22603 Hamburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Perbandt
authors.affiliation: the Departments of Chemical Sciences and Technologies, 00133 Rome, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Stella
authors.affiliation: Biology, University of Rome "Tor Vergata," 00133 Rome, Italy.
authors.forename: Jens Z
authors.initials: JZ
authors.lastname: Pedersen
authors.affiliation: Department of Biology, University of Rome "Roma Tre," 00146 Rome, Italy; Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina 27708.
authors.forename: Alessio
authors.initials: A
authors.lastname: Bocedi
authors.affiliation: Biology, University of Rome "Tor Vergata," 00133 Rome, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Petrarca
authors.affiliation: Childrens Hospital "Bambin Gesù," 00165 Rome, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Federici
authors.affiliation: the Departments of Chemical Sciences and Technologies, 00133 Rome, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Ricci
mesh_terms: D000818:Animals; D001665:Binding Sites; D019281:Dimerization; D005978:Glutathione / Q000737:chemistry; D005982:Glutathione Transferase / Q000378:metabolism*; D006427:Hemin / Q000737:chemistry; D007700:Kinetics; D008954:Models, Biological; D008968:Molecular Conformation; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010084:Oxidation-Reduction; D010963:Plasmodium falciparum / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D006427:Hemin; D005982:Glutathione Transferase; D005978:Glutathione