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論文 |
論文
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Kataoka, Kunishige ; Komori, Hirofumi ; Ueki, Yusaku ; Konno, Yusuke ; Kamitaka, Yuji ; Kurose, Shinji ; Tsujimura, Seiya ; Higuchi, Yoshiki ; Kano, Kenji ; Seo, Daisuke ; Sakurai, Takeshi
概要:
金沢大学大学院自然科学研究科物質創成<br />金沢大学理学部<br />CueO is a multicopper oxidase (MCO) that is involved in the homeostasis of Cu in Es
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cherichia coli and is the sole cuprous oxidase to have ever been found. Differing from other MCOs, the substrate-binding site of CueO is deeply buried under a methionine-rich helical region including α-helices 5, 6, and 7 that interfere with the access of organic substrates. We deleted the region Pro357-His406 and replaced it with a Gly-Gly linker. The crystal structures of a truncated mutant in the presence and in the absence of excess Cu(II) indicated that the scaffold of the CueO molecule and metal-binding sites were reserved in comparison with those of CueO. In addition, the high thermostability of the protein molecule and its spectroscopic and magnetic properties due to four Cu centers were also conserved after truncation. As for functions, the cuprous oxidase activity of the mutant was reduced to ca 10% that of recombinant CueO owing to the decrease in the affinity of the labile Cu site for Cu(I) ions, although activities for laccase substrates such as 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), p-phenylenediamine, and 2,6-dimethoxyphenol increased due to changes in the access of these organic substrates to the type I Cu site. The present engineering of CueO indicates that the methionine-rich α-helices function as a barrier to the access of bulky organic substrates, which provides CueO with specificity as a cuprous oxidase. © 2007 Elsevier Ltd. All rights reserved.
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論文 |
論文
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Kurose, Shinji ; Kataoka, Kunishige ; Shinohara, Naoya ; Miura, Yuko ; Tsutsumi, Maiko ; Tsujimura, Seiya ; Kano, Kenji ; Sakurai, Takeshi
概要:
Replacement of Met510, the axial ligand to the type I Cu in a cuprous oxidase CueO, with Leu afforded the three-coordinated type I Cu, while Gln, Ala, and Thr mutations led to the replacement of the thioether ligand with oxygen ligands
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(amide carbonyl group and water), and characteristic properties of absorption, circular dichroism, and electron paramagnetic resonance spectra of a variety of Met510 mutants were correlated with the changes in redox potential and enzyme activities.
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