title: A tRNA-dependent cysteine biosynthesis enzyme recognizes the selenocysteine-specific tRNA in Escherichia coli.
abstract: The essential methanogen enzyme Sep-tRNA:Cys-tRNA synthase (SepCysS) converts O-phosphoseryl-tRNA(Cys) (Sep-tRNA(Cys)) into Cys-tRNA(Cys) in the presence of a sulfur donor. Likewise, Sep-tRNA:Sec-tRNA synthase converts O-phosphoseryl-tRNA(Sec) (Sep-tRNA(Sec)) to selenocysteinyl-tRNA(Sec) (Sec-tRNA(Sec)) using a selenium donor. While the Sep moiety of the aminoacyl-tRNA substrates is the same in both reactions, tRNA(Cys) and tRNA(Sec) differ greatly in sequence and structure. In an Escherichia coli genetic approach that tests for formate dehydrogenase activity in the absence of selenium donor we show that Sep-tRNA(Sec) is a substrate for SepCysS. Since Sec and Cys are the only active site amino acids known to sustain FDH activity, we conclude that SepCysS converts Sep-tRNA(Sec) to Cys-tRNA(Sec), and that Sep is crucial for SepCysS recognition.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Yuan
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hohn
authors.forename: R Lynn
authors.initials: RL
authors.lastname: Sherrer
authors.forename: Sotiria
authors.initials: S
authors.lastname: Palioura
authors.forename: Dan
authors.initials: D
authors.lastname: Su
authors.forename: Dieter
authors.initials: D
authors.lastname: Söll
mesh_terms: D001483:Base Sequence; D003545:Cysteine / Q000096:biosynthesis*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005560:Formate Dehydrogenases / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D013379:Substrate Specificity / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D012346:RNA, Transfer, Amino Acyl; C112705:selenocysteinyl-tRNA; D005560:Formate Dehydrogenases; D003545:Cysteine