Q-Band Electron-Nuclear Double Resonance Reveals Out-of-Plane Hydrogen Bonds Stabilize an Anionic Ubisemiquinone in Cytochrome bo₃ from Escherichia coli.

ABSTRACT: The respiratory cytochrome bo₃ ubiquinol oxidase from Escherichia coli has a high-affinity ubiquinone binding site that stabilizes the one-electron reduced ubisemiquinone (SQ_H), which is a transient intermediate during the electron-mediated reduction of O₂ to water. It is known that SQ_H is stabilized by two strong hydrogen bonds from R71 and D75 to ubiquinone carbonyl oxygen O1 and weak hydrogen bonds from H98 and Q101 to O4. In this work, SQ_H was investigated with orientation-selective Q-band (∼34 GHz) pulsed ¹H electron-nuclear double resonance (ENDOR) spectroscopy on fully deuterated cytochrome (cyt) bo₃ in a H₂O solvent so that only exchangeable protons contribute to the observed ENDOR spectra. Simu

SUBMITTER: Sun C 

PROVIDER: S-EPMC5558440 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature