School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom.
Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, United Kingdom.
Proc Natl Acad Sci U S A. 2020 Mar 24;117(12):6484-6490. doi: 10.1073/pnas.1918936117. Epub 2020 Mar 9.
In redox metalloenzymes, the process of electron transfer often involves the concerted movement of a proton. These processes are referred to as proton-coupled electron transfer, and they underpin a wide variety of biological processes, including respiration, energy conversion, photosynthesis, and metalloenzyme catalysis. The mechanisms of proton delivery are incompletely understood, in part due to an absence of information on exact proton locations and hydrogen bonding structures in a bona fide metalloenzyme proton pathway. Here, we present a 2.1-Å neutron crystal structure of the complex formed between a redox metalloenzyme (ascorbate peroxidase) and its reducing substrate (ascorbate). In the neutron structure of the complex, the protonation states of the electron/proton donor (ascorbate) and all of the residues involved in the electron/proton transfer pathway are directly observed. This information sheds light on possible proton movements during heme-catalyzed oxygen activation, as well as on ascorbate oxidation.
在氧化还原金属酶中，电子转移过程通常涉及质子的协同运动。这些过程被称为质子耦合电子转移，它们是多种生物过程的基础，包括呼吸、能量转换、光合作用和金属酶催化。质子传递的机制尚不完全清楚，部分原因是缺乏关于真正氧化还原金属酶质子途径中确切质子位置和氢键结构的信息。在这里，我们展示了一种氧化还原金属酶（抗坏血酸过氧化物酶）与其还原底物（抗坏血酸）形成的复合物的 2.1Å 中子晶体结构。在复合物的中子结构中，可以直接观察到电子/质子供体（抗坏血酸）的质子化状态以及参与电子/质子转移途径的所有残基。这些信息揭示了在血红素催化的氧气活化过程中可能发生的质子运动，以及抗坏血酸氧化过程。
