title: Mitochondrial targeting of glutathione reductase requires a leader sequence.
abstract: Glutathione reductase (GR), which catalyzes the conversion of glutathione disulfide to glutathione, is encoded in nuclear DNA, but is active in cytoplasm and mitochondria. However, analyses of known protein and DNA sequences for human GR have not revealed a potential mitochondrial targeting signal (MTS). We generated two 5'-truncated GR clones, which resulted in omission of the N-terminal 5 or 10 amino acids, to disable a potential targeting signal, and generated two GR clones containing synthetic MTS cDNAs. Transfection of Chinese hamster ovary cells with the full length human GR cDNA or with the 5'-truncated clones increased cytosolic GR activities 6- to 14-fold, but increased mitochondrial activities less than 2-fold. In contrast, transfection with either of the GR clones containing MTS cDNAs increased GR activities in mitochondria more than 24-fold. We conclude that the existing protein and DNA sequences for human GR do not contain a MTS and that such a signal is needed for effective mitochondrial targeting.
authors.affiliation: Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: T
authors.initials: T
authors.lastname: Tamura
authors.forename: H W
authors.initials: HW
authors.lastname: McMicken
authors.forename: C V
authors.initials: CV
authors.lastname: Smith
authors.forename: T N
authors.initials: TN
authors.lastname: Hansen
mesh_terms: D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002451:Cell Compartmentation; D006224:Cricetinae; D017931:DNA Primers / Q000737:chemistry; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D017931:DNA Primers; D005980:Glutathione Reductase; D005978:Glutathione