%0 Journal Article
%T Demethylmenaquinol is a substrate of Escherichia coli nitrate reductase A (NarGHI) and forms a stable semiquinone intermediate at the NarGHI quinol oxidation site
%+ Aix Marseille Université (AMU)
%+ Bioénergétique et Ingénierie des Protéines (BIP )
%+ Université Pierre et Marie Curie - Paris 6 (UPMC)
%+ UPMC - UFR Sciences de la vie (UFR 927 )
%+ Laboratoire de chimie bactérienne (LCB)
%+ Institut méditerranéen d'océanologie (MIO)
%+ Laboratoire Adaptation et pathogénie des micro-organismes [Grenoble] (LAPM)
%A Rendon, Julia
%A Pilet, Eric
%A Fahs, Zeinab
%A Seduk, Farida
%A Sylvi, Léa
%A Chehade, Mahmoud Hajj
%A Pierrel, Fabien
%A Guigliarelli, Bruno
%A Magalon, Axel
%A Grimaldi, Stephane
%< avec comité de lecture
%@ 0005-2728
%J Biochimica biophysica acta (BBA) - Bioenergetics
%I Elsevier
%V 1847
%N 8
%P 739-747
%8 2015-08
%D 2015
%R 10.1016/j.bbabio.2015.05.001
%K semiquinone
%K EPR spectroscopy
%K Protein Cofactor interactions
%K Nitrate reductase
%K Electron transfers
%Z Chemical Sciences
%Z Life Sciences [q-bio]Journal articles
%X Quinones are essential building blocks of respiration, a universal process dedicated to efficient harvesting of environmental energy and its conversion into a transmembrane chemiosmotic potential. Quinones differentiate mostly by their midpoint redox potential. As such, γ-proteobacteria such as Escherichia coli are characterized by the presence of demethylmenaquinone (DMK) with an intermediate redox potential between low-potential (menaquinone) and high-potential (ubiquinone) quinones. In this study, we show that demethylmenaquinol (DMKH2) is a good substrate for nitrate reductase A (NarGHI) in nitrate respiration in E. coli. Kinetic studies performed with quinol analogs on NarGHI show that removal of the methyl group on the naphthoquinol ring impacts modestly the catalytic constant but not the KM. EPR-monitored redox titrations of NarGHI-enriched membrane vesicles reveal that endogeneous demethylmenasemiquinone (DMSK) intermediates are stabilized in the enzyme. The measured midpoint potential of the DMK/DMKH2 redox couple in NarGHI (E′m,7.5 (DMK/DMKH2) ~− 70 mV) is significantly lower than that previously measured for unbound species. High resolution pulsed EPR experiments demonstrate that DMSK are formed within the NarGHI quinol oxidation site. Overall, our results provide the first characterization of a protein-bound DMSK and allows for comparison for distinct use of three quinones at a single Q-site in NarGHI.
%G English
%L hal-01429032
%U https://hal.science/hal-01429032
%~ INSU
%~ UPMC
%~ UGA
%~ UNIV-TLN
%~ CNRS
%~ UNIV-GRENOBLE1
%~ UNIV-AMU
%~ MIO
%~ OSU-INSTITUT-PYTHEAS
%~ TIMC-IMAG-GEM
%~ SORBONNE-UNIVERSITE
%~ AMIDEX
%~ SU-MEDECINE
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%~ ALLIANCE-SU