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An Oxidoreductase AioE is Responsible for Bacterial Arsenite Oxidation and Resistance

Qian Wang, Yushan Han, Kaixiang Shi, Xia Fan, Lu Wang, Mingshun Li & Gejiao Wang

Previously, we found that arsenite (AsIII) oxidation could improve the generation of ATP/NADH to
support the growth of Agrobacterium tumefaciens GW4. In this study, we found that aioE is induced
by AsIII and located in the arsenic island near the AsIII oxidase genes aioBA and co-transcripted with
the arsenic resistant genes arsR1-arsC1-arsC2-acr3-1. AioE belongs to TrkA family corresponding
the electron transport function with the generation of NADH and H+. An aioE in-frame deletion
strain showed a null AsIII oxidation and a reduced AsIII resistance, while a cytC mutant only reduced
AsIII oxidation efficiency. With AsIII, aioE was directly related to the increase of NADH, while cytC was
essential for ATP generation. In addition, cyclic voltammetry analysis showed that the redox potential
(ORP) of AioBA and AioE were +0.297 mV vs. NHE and +0.255 mV vs. NHE, respectively. The ORP
gradient is AioBA > AioE > CytC (+0.217 ~ +0.251 mV vs. NHE), which infers that electron may transfer
from AioBA to CytC via AioE. The results indicate that AioE may act as a novel AsIII oxidation electron
transporter associated with NADH generation. Since AsIII oxidation contributes AsIII detoxification, the
essential of AioE for AsIII resistance is also reasonable.



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