title: A selenocysteine-containing peroxiredoxin from the strictly anaerobic organism Eubacterium acidaminophilum.
abstract: A strongly 75Se-labeled 22 kDa protein detected previously showed in its N-terminal sequence the highest similarity to the family of thiol-dependent peroxidases, now called peroxiredoxins. The respective gene prxU was cloned and analyzed. prxU encodes a protein of 203 amino acids (22,470 Da) and contains an in-frame UGA codon (selenocysteine) at the position of the so far strictly conserved and catalytically active Cys47. The second conserved cysteine present in 2-Cys peroxiredoxins was replaced by alanine. Heterologous expression of the Eubacterium acid-aminophilum PrxU as a recombinant selenoprotein in Escherichia coli was not possible. A cysteine-encoding mutant gene, prxU47C, containing UGC instead of UGA was strongly expressed. This recombinant PrxU47C mutant protein was purified to homogeneity by its affinity tag, but was not active as a thiol-dependent peroxidase. The identification of prxU reveals that the limited class of natural selenoproteins may in certain organisms also include isoenzymes of peroxiredoxins, previously only known as non-selenoproteins containing catalytic cysteine residues.
authors.affiliation: Institut für Mikrobiologie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Söhling
authors.forename: T
authors.initials: T
authors.lastname: Parther
authors.forename: K P
authors.initials: KP
authors.lastname: Rücknagel
authors.forename: M A
authors.initials: MA
authors.lastname: Wagner
authors.forename: J R
authors.initials: JR
authors.lastname: Andreesen
mesh_terms: D019943:Amino Acid Substitution; D000975:Antioxidants / Q000737:chemistry; D001483:Base Sequence; D003001:Cloning, Molecular; D005051:Eubacterium / Q000201:enzymology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D054464:Peroxiredoxins; D017279:Selenocysteine; D016415:Sequence Alignment
chemical_list: D000975:Antioxidants; D017279:Selenocysteine; D006861:Hydrogen Peroxide; D010544:Peroxidases; D054464:Peroxiredoxins