title: Nitrosocyanin, a red cupredoxin-like protein from Nitrosomonas europaea.
abstract: Nitrosocyanin (NC), a soluble, red Cu protein isolated from the ammonia-oxidizing autotrophic bacterium Nitrosomonas europaea, is shown to be a homo-oligomer of 12 kDa Cu-containing monomers. Oligonucleotides based on the amino acid sequence of the N-terminus and of the C-terminal tryptic peptide were used to sequence the gene by PCR. The translated protein sequence was significantly homologous with the mononuclear cupredoxins such as plastocyanin, azurin, or rusticyanin, the type 1 copper-binding region of nitrite reductase, and the binuclear CuA binding region of N(2)O reductase or cytochrome oxidase. The gene for NC contains a leader sequence indicating a periplasmic location. Optical bands for the red Cu center at 280, 390, 500, and 720 nm have extinction coefficients of 13.9, 7.0, 2.2, and 0.9 mM(-1), respectively. The reduction potential of NC (85 mV vs SHE) is much lower than those for known cupredoxins. Sequence alignments with homologous blue copper proteins suggested copper ligation by Cys95, His98, His103, and Glu60. Ligation by these residues (and a water), a trimeric protein structure, and a cupredoxin beta-barrel fold have been established by X-ray crystallography of the protein [Lieberman, R. L., Arciero, D. M., Hooper, A. B., and Rosenzweig, A. C. (2001) Biochemistry 40, 5674-5681]. EPR spectra of the red copper center indicated a Cu(II) species with a g(parallel) of 2.25 and an A(parallel) of 13.8 mT (144 x 10(-4) cm(-1)), typical of Cu in a type 2 copper environment. NC is the first example of a type 2 copper center in a cupredoxin fold. The open coordination site and type 2 copper suggest a possible catalytic rather than electron transfer function.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, Minnesota 55108, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Arciero
authors.forename: Brad S
authors.initials: BS
authors.lastname: Pierce
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hendrich
authors.forename: Alan B
authors.initials: AB
authors.lastname: Hooper
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D003001:Cloning, Molecular; D003300:Copper / Q000032:analysis; D004269:DNA, Bacterial / Q000235:genetics; D004578:Electron Spin Resonance Spectroscopy; D005798:Genes, Bacterial; D008667:Metalloproteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009606:Nitrosomonas / Q000737:chemistry* / Q000235:genetics*; D010088:Oxidoreductases / Q000235:genetics; D010970:Plastocyanin / Q000235:genetics; D020836:Protein Structure, Quaternary; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008667:Metalloproteins; C431624:red copper protein, Nitrosomonas europaea; D003300:Copper; D010970:Plastocyanin; D010088:Oxidoreductases; C022763:nitrous oxide reductase