A Eukaryotic Copper-Containing Nitrite Reductase Derived from a NirK Homolog Gene of Aspergillus oryzae

Yoshito NAKANISHI; Shengmin ZHOU; Sang-Wan KIM; Shinya FUSHINOBU; Jun-ichi MARUYAMA; Katsuhiko KITAMOTO; Takayoshi WAKAGI; Hirofumi SHOUN

doi:10.1271/bbb.90844

Biochemistry & Molecular Biology Regular Papers

A Eukaryotic Copper-Containing Nitrite Reductase Derived from a NirK Homolog Gene of Aspergillus oryzae

Yoshito NAKANISHI, Shengmin ZHOU, Sang-Wan KIM, Shinya FUSHINOBU, Jun-ichi MARUYAMA, Katsuhiko KITAMOTO, Takayoshi WAKAGI, Hirofumi SHOUN

Author information

Yoshito NAKANISHI
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo
Shengmin ZHOU
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo
Sang-Wan KIM
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo
Shinya FUSHINOBU
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo
Jun-ichi MARUYAMA
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo
Katsuhiko KITAMOTO
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo
Takayoshi WAKAGI
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo
Hirofumi SHOUN
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo

Keywords: nitrite reductase, copper-containing dNiR, denitrification, mitochondria, cytochrome P450 nitric oxide reductase

JOURNAL FREE ACCESS

2010 Volume 74 Issue 5 Pages 984-991

DOI https://doi.org/10.1271/bbb.90844

View "Advance Publication" version (May 7, 2010).

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Abstract

We cloned a bacterial copper-containing nitrite reductase (NirK) homolog gene of Aspergillus oryzae (AonirK). Alignment showed that amino acid residues crucial for copper binding are conserved in the deduced sequence of the fungal protein. The recombinant protein exhibited distinct nitrite reductase activity, and its absorption and EPR spectra showed the presence of type 1 and type 2 copper atoms in the molecule. AonirK transcriptionally responded to denitrification conditions. Although the denitrifying activity of A. oryzae was weak under the conditions employed, high expression of the gene in the fungal cells enhanced the denitrifying activity 6-fold, accompanied by distinct cell growth. Furthermore, the highly expressed AoNirK was subcellularly localized to the mitochondria. The results demonstrated that AoNirK is responsible for fungal denitrification. Discussion is added on the novel insight concerning the origin and evolution of the mitochondrion provided by the findings for eukaryotic NirKs.

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