論文

査読有り 国際誌
2009年12月

Inhibition of electron acceptance from ascorbate by the specific N-carbethoxylations of maize cytochrome b561: a common mechanism for the transmembrane electron transfer in cytochrome b561 protein family.

Journal of biochemistry
  • Nobuyuki Nakanishi
  • ,
  • Md Motiur Rahman
  • ,
  • Yoichi Sakamoto
  • ,
  • Masahiro Miura
  • ,
  • Fusako Takeuchi
  • ,
  • Sam-Yong Park
  • ,
  • Motonari Tsubaki

146
6
開始ページ
857
終了ページ
66
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1093/jb/mvp146

Cytochromes b(561) constitute a novel class of proteins in eukaryotic cells with a number of highly relevant common features including six transmembrane alpha-helices and two haem groups. Of particular interest is the presence of a large number of plant homologues having putative ascorbate- and monodehydroascorbate radical-binding sites. We conducted a diethylpyrocarbonate-modification study employing Zea mays cytochrome b(561) heterologously expressed in Pichia pastoris cells. Pre-treatment of cytochrome b(561) with diethylpyrocarbonate in oxidized form caused N-carbethoxylation of His(86), His(159) and Lys(83), leading to a drastic inhibition of the electron transfer from ascorbate. The activity was protected by the inclusion of ascorbate during the treatment. However, midpoint potentials of two haem centres did show only slight decreases upon the treatment, suggesting that changes in the midpoint potentials were not the major cause of the inhibition. Present results indicated that Zea mays cytochrome b(561) conducted an ascorbate-specific transmembrane electron transfer by utilizing a concerted H(+)/e(-) transfer mechanism and that the specific N-carbethoxylation of haem axial His(86) that would inhibit the removal of a proton from the bound ascorbate was a major cause of the inhibition. On the other hand, Lys(83) might be important for an initial step(s) of the fast electron acceptance from ascorbate.

リンク情報
DOI
https://doi.org/10.1093/jb/mvp146
PubMed
https://www.ncbi.nlm.nih.gov/pubmed/19762344