title: Three distinct-type glutathione S-transferases from Escherichia coli important for defense against oxidative stress.
abstract: Previously, we characterized glutathione S-transferase (GST) B1-1 from Escherichia coli enzymologically and structurally. Besides GST B1-1, E. coli has seven genes that encode GST-like proteins, for which, except SspA, neither biological roles nor biochemical properties are known. Here we show that the GST-like YfcF and YfcG proteins have low but significant GSH-conjugating activity toward 1-chloro-2,4-dinitorobenzene and GSH-dependent peroxidase activity toward cumene hydroperoxide. Analysis involving site-directed mutagenesis suggested that Ser16 and Asn11 were important for the activities of YfcF and YfcG, respectively. On the contrary, no residue around the catalytic site of GST B1-1 has been demonstrated to be essential for catalytic activity. Deletions of the gst, yfcF, and yfcG genes each decreased the resistibility of the bacteria to hydrogen peroxide, which was recovered by transformation with the expression plasmid for the deleted enzyme. The inactive YfcF(S16G) and YfcG(N11A) mutants, however, could not rescue the knockout bacteria. Thus, E. coli has at least three GSTs of distinct classes, all of which are important for defense against oxidative stress in spite of the structural diversity. This seems consistent with the hypothesis that GSTs constitute a protein superfamily that has evolved from a thioredoxin-like ancestor in response to the development of oxidative stress.
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392.
authors.forename: Takuya
authors.initials: T
authors.lastname: Kanai
authors.forename: Kenji
authors.initials: K
authors.lastname: Takahashi
authors.forename: Hideshi
authors.initials: H
authors.lastname: Inoue
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis*; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018384:Oxidative Stress / Q000187:drug effects*; D016415:Sequence Alignment
chemical_list: D029968:Escherichia coli Proteins; D006861:Hydrogen Peroxide; D005982:Glutathione Transferase; C515863:YfcF protein, E coli; C515864:YfcG protein, E coli