Identification of a Novel Chromate and Selenite Reductase FesR in Alishewanella sp. WH16-1

Zijie Zhou; Lin Zhu; Yixuan Dong; Lexing You; Shixue Zheng; Gejiao Wang; Xian Xia

doi:10.3389/fmicb.2022.834293

Identification of a Novel Chromate and Selenite Reductase FesR in Alishewanella sp. WH16-1

Front Microbiol. 2022 Mar 8:13:834293. doi: 10.3389/fmicb.2022.834293. eCollection 2022.

Authors

Zijie Zhou¹, Lin Zhu¹, Yixuan Dong¹, Lexing You², Shixue Zheng¹, Gejiao Wang¹, Xian Xia^{1

3}

Affiliations

¹ State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China.
² College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, China.
³ Hubei Key Laboratory of Edible Wild Plants Conservation & Utilization, Huangshi Key Laboratory of Lake Environmental Protection and Sustainable Utilization of Resources, Hubei Engineering Research Center of Characteristic Wild Vegetable Breeding and Comprehensive Utilization Technology, College of Life Sciences, Hubei Normal University, Huangshi, China.

Abstract

A ferredoxin protein (AAY72_06850, named FesR) was identified to associate with chromate [Cr(VI)] resistance in Alishewanella sp. WH16-1. FesR and its similar proteins were phylogenetically separated from other reductase families. Unlike the reported Cr(VI) and selenite [Se(IV)] reductases, two 4Fe-4S clusters and one flavin adenine dinucleotide (FAD) -binding domain were found in the FesR sequence. The experiment in vivo showed that the mutant strain ΔfesR had lost partial Cr(VI) and Se(IV) reduction capacities compared to the wild-type and complemented strains. Furthermore, overexpression in Escherichia coli and enzymatic tests in vitro showed FesR were involved in Cr(VI) and Se(IV) reduction. 4Fe-4S cluster in purified FesR was detected by ultraviolet-visible spectrum (UV-VIS) and Electron Paramagnetic Resonance (EPR). The Km values of FesR for Cr(VI) and Se(IV) reduction were 1682.0 ± 126.2 and 1164.0 ± 89.4 μmol/L, and the Vmax values for Cr(VI) and Se(IV) reduction were 4.1 ± 0.1 and 9.4 ± 0.3 μmol min^-1 mg^-1, respectively. Additionally, site-directed mutagenesis and redox potential analyses showed that 4Fe-4S clusters were essential to FesR, and FAD could enhance the enzyme efficiencies of FesR as intracellular electron transporters. To the best of our knowledge, FesR is a novel Cr(VI) and Se(IV) reductase.

Keywords: Alishewanella; FesR; chromate reduction; electron transport; selenite reduction.