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Role of conserved arginine in the heme distal site of HutZ from Vibrio cholerae in the heme degradation reaction

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Title: Role of conserved arginine in the heme distal site of HutZ from Vibrio cholerae in the heme degradation reaction
Authors: Uchida, Takeshi Browse this author →KAKEN DB
Dojun, Nobuhiko Browse this author
Ota, Kazuki Browse this author
Sekine, Yukari Browse this author
Nakamura, Yuina Browse this author
Umetsu, Sayaka Browse this author
Ishimori, Koichiro Browse this author →KAKEN DB
Keywords: Heme
Vibrio cholerae
Heme oxygenase
Reaction mechanism
Issue Date: 30-Nov-2019
Publisher: Elsevier
Journal Title: Archives of Biochemistry and Biophysics
Volume: 677
Start Page: 108165
Publisher DOI: 10.1016/
Abstract: HutZ from Vibrio cholerae is a dimeric enzyme that catalyzes degradation of heme. The highly conserved Arg92 residue in the HutZ family is proposed to interact with an iron-bound water molecule in the distal heme pocket. To clarify the specific role of Arg92 in the heme degradation reaction, the residue was substituted with alanine, leucine, histidine or lysine to modulate electrostatic interactions with iron-bound ligand. All four Arg92 mutants reacted with hydrogen peroxide to form verdoheme, a prominent intermediate in the heme degradation process. However, when ascorbic acid was used as an electron source, iron was not released even at pH 6.0 despite a decrease in the Soret band, indicating that non-enzymatic heme degradation occurred. Comparison of the rates of heme reduction, ligand binding and verdoheme formation suggested that proton transfer to the reduced oxyferrous heme, a potential rate-limiting step of heme degradation in HutZ, is hampered by mutation. In our previous study, we found that the increase in the distance between heme and Trp109 from 16 to 18 Å upon lowering the pH from 8.0 to 6.0 leads to activation of ascorbic acid-assisted heme degradation by HutZ. The distance in Arg92 mutants was >19 Å at pH 6.0, suggesting that subunit-subunit interactions at this pH are not suitable for heme degradation, similar to Asp132 and His63 mutants. These results suggest that interactions of Arg92 with heme-bound ligand induce alterations in the distance between subunits, which plays a key role in controlling the heme degradation activity of HutZ.
Rights: ©2019.This manuscript version is made available under the CC-BY-NC-ND 4.0 license
Type: article (author version)
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 内田 毅

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