title: A pseudo-phytochelatin synthase in the ciliated protozoan Tetrahymena thermophila.
abstract: Phytochelatins (PCs) and metallothioneins (MTs) are the two major heavy metal chelating peptides in eukaryotes. We report here on the identification of a biosynthetically inactive pseudo-phytochelatin synthase enzyme (TtpsiPCS) in the ciliate Tetrahymena thermophila, the first of this kind (pseudo-PCS) to be described in eukaryotes. TtpsiPCS which resembles a true PCS at the N-terminal region, while it is most divergent in its Cys-poor C-terminal region, was found to be up-regulated under cadmium stress conditions. However, only glutathione (GSH) hydrolysis products, but not PCs, could be detected in extracts from Cd-treated cells. The latter feature is reminiscent of pseudo-PCS enzymes recently identified in cyanobacteria, which are also biosynthetically inactive, but capable to hydrolyze GSH.
authors.affiliation: Departamento de Microbiología-III, Facultad de Biología, Universidad Complutense (UCM), 28040 Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Amaro
authors.forename: Roberta
authors.initials: R
authors.lastname: Ruotolo
authors.forename: Ana
authors.initials: A
authors.lastname: Martín-González
authors.forename: Andrea
authors.initials: A
authors.lastname: Faccini
authors.forename: Simone
authors.initials: S
authors.lastname: Ottonello
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Gutiérrez
mesh_terms: D019881:Aminoacyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D019256:Cadmium Chloride / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D054811:Phytochelatins / Q000096:biosynthesis; D016808:Tetrahymena thermophila / Q000187:drug effects / Q000201:enzymology*
chemical_list: D054811:Phytochelatins; D019881:Aminoacyltransferases; C093784:glutathione gamma-glutamylcysteinyltransferase; D005978:Glutathione; D019256:Cadmium Chloride