CuB promotes both binding and reduction of dioxygen at the heme-copper binuclear center in the Escherichia coli bo-type ubiquinol oxidase |
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Authors: | Tatsushi Mogi Tomoyasu Hirano Hiro Nakamura Yasuhiro Anraku Yutaka Orii |
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Institution: | aDepartment of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan;bInstitute of Physical and Chemical Research (RIKEN), Hirosawa, Wako, Saitama 351-01, Japan;cDepartment of Public Health, Graduate School of Medicine, Kyoto University, Kyoto 606, Japan |
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Abstract: | A CuB-deficient mutant of the Escherichia coli bo-type ubiquinol oxidase exhibits a very low oxidase activity that is consistent with a decreased dioxygen binding rate. During the turnover, a photolabile reaction intermediate persists for a few hundred milliseconds, due to much slower heme o-to-ligand electron transfer. Thus, the lack of CuB seems to have endowed the mutant enzyme with myoglobin-like properties, thereby stabilizing the CO-bound form, too. Accordingly we conclude that CuB plays a pivotal role in preferential trapping and efficient reduction of dioxygen at the heme-copper binuclear center. |
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Keywords: | E coli bo-type ubiquinol oxidase Heme-copper binuclear center CuB-deficient mutant Intramolecular electron transfer Dioxygen reduction chemistry |
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