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The Ubiquinol Binding Site of Cytochrome bo3 from Escherichia coli Accommodates Menaquinone and Stabilizes a Functional Menasemiquinone.
Biochemistry ( IF 2.9 ) Pub Date : 2019-11-04 , DOI: 10.1021/acs.biochem.9b00750 Ziqiao Ding 1 , Chang Sun 1 , Sophia M Yi 1 , Robert B Gennis 1, 2 , Sergei A Dikanov 3
Biochemistry ( IF 2.9 ) Pub Date : 2019-11-04 , DOI: 10.1021/acs.biochem.9b00750 Ziqiao Ding 1 , Chang Sun 1 , Sophia M Yi 1 , Robert B Gennis 1, 2 , Sergei A Dikanov 3
Affiliation
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Cytochrome bo3, one of three terminal oxygen reductases in the aerobic respiratory chain of Escherichia coli, has been well characterized as a ubiquinol oxidase. The ability of cytochrome bo3 to catalyze the two-electron oxidation of ubiquinol-8 requires the enzyme to stabilize the one-electron oxidized ubisemiquinone species that is a transient intermediate in the reaction. Cytochrome bo3 has been shown recently to also utilize demethylmenaquinol-8 as a substrate that, along with menaquinol-8, replaces ubiquinol-8 when E. coli is grown under microaerobic or anaerobic conditions. In this work, we show that its steady-state turnover with 2,3-dimethyl-1,4-naphthoquinol, a water-soluble menaquinol analogue, is just as efficient as with ubiquinol-1. Using pulsed electron paramagnetic resonance spectroscopy, we demonstrate that the same residues in cytochrome bo3 that stabilize the semiquinone state of ubiquinone also stabilize the semiquinone state of menaquinone, with the hydrogen bond strengths and the distribution of unpaired spin density accommodated for the different substrate. Catalytic function with menaquinol is more tolerant of mutations at the active site than with ubiquinol. A mutation of one of the stabilizing residues (R71H in subunit I) that eliminates the ubiquinol oxidase activity of cytochrome bo3 does not abolish activity with soluble menaquinol analogues.
中文翻译：
来自大肠杆菌的细胞色素bo3的泛醇结合位点可容纳甲萘醌并稳定功能性甲萘醌。
细胞色素bo 3是大肠杆菌有氧呼吸链中三个末端氧还原酶之一，已被很好地表征为泛醇氧化酶。细胞色素bo 3催化泛醇8的两电子氧化的能力要求该酶稳定单电子氧化的泛半醌物质，后者是反应中的过渡中间体。最近显示，细胞色素bo 3还利用去甲基甲萘醌8作为底物，与甲萘醌8一起替代大肠杆菌时的泛醇8 。在微需氧或厌氧条件下生长。在这项工作中，我们证明了其与2,3-二甲基-1,4-萘喹啉（一种水溶性薄荷醇类似物）的稳态转化率与泛醌1一样高效。使用脉冲电子顺磁共振波谱，我们证明了细胞色素bo 3中稳定泛醌半醌状态的相同残基也稳定了甲基萘醌的半醌状态，氢键强度和不成对自旋密度的分布适用于不同的底物。甲萘醌的催化功能比泛醇对活性位点的突变具有更大的耐受性。稳定残基之一（亚基I中的R71H）的突变消除了细胞色素的泛醇氧化酶活性bo 3不会消除可溶性甲萘醌类似物的活性。
更新日期：2019-11-04
中文翻译：
来自大肠杆菌的细胞色素bo3的泛醇结合位点可容纳甲萘醌并稳定功能性甲萘醌。
细胞色素bo 3是大肠杆菌有氧呼吸链中三个末端氧还原酶之一，已被很好地表征为泛醇氧化酶。细胞色素bo 3催化泛醇8的两电子氧化的能力要求该酶稳定单电子氧化的泛半醌物质，后者是反应中的过渡中间体。最近显示，细胞色素bo 3还利用去甲基甲萘醌8作为底物，与甲萘醌8一起替代大肠杆菌时的泛醇8 。在微需氧或厌氧条件下生长。在这项工作中，我们证明了其与2,3-二甲基-1,4-萘喹啉（一种水溶性薄荷醇类似物）的稳态转化率与泛醌1一样高效。使用脉冲电子顺磁共振波谱，我们证明了细胞色素bo 3中稳定泛醌半醌状态的相同残基也稳定了甲基萘醌的半醌状态，氢键强度和不成对自旋密度的分布适用于不同的底物。甲萘醌的催化功能比泛醇对活性位点的突变具有更大的耐受性。稳定残基之一（亚基I中的R71H）的突变消除了细胞色素的泛醇氧化酶活性bo 3不会消除可溶性甲萘醌类似物的活性。
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