Escherichia coli Uses Separate Enzymes to Produce H2S and Reactive Sulfane Sulfur From L-cysteine.

Huaiwei Liu,Yongzhen Xia,Luying Xun,Kai Li,Rui Zhao,Guanhua Xuan,Yufeng Xin

doi:10.3389/fmicb.2019.00298

Huaiwei Liu, Yongzhen Xia + Show 5 more

Open Access

https://doi.org/10.3389/fmicb.2019.00298

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Abstract

Hydrogen sulfide (H2S) has been proposed to have various physiological functions, and it may function through reactive sulfane sulfur. Since the two sulfur forms often coexist, they are normally considered interchangeable. Here, we characterized the production of H2S and reactive sulfane sulfur in Escherichia coli MG1655 and found that they are not readily interchangeable. They are primarily produced from L-cysteine via different enzymes. L-Cysteine desulfhydrases consumed L-cysteine and directly generated H2S. The produced H2S was mainly lost through evaporation into the gas phase, as E. coli does not have enzymes that easily oxidize H2S to reactive sulfane sulfur. L-Cysteine desulfhydrases were also responsible for the degradation of exogenous L-cysteine, which is toxic at high levels. Conversely, L-cysteine aminotransferase and 3-mercaptopyruvate sulfurtransferase sequentially metabolized endogenous L-cysteine to produce cellular reactive sulfane sulfur; however, it was not a major route of H2S production during normal growth or during the metabolism of exogenous L-cysteine by the resting cells. Noticeably, the 3-mercaptopyruvate sulfurtransferase mutant contained less reactive sulfane sulfur and displayed a greater sensitivity to H2O2 than did the wild type. Thence, reactive sulfane sulfur is likely a common cellular component, involved in protein sulfhydration and protecting cells from oxidative stress.

Highlights

H2S may protect bacterial cells from oxidative stress (Shatalin et al, 2011) and have physiological roles in cellular signaling through protein sulfhydration (Paul and Snyder, 2012; Giedroc, 2017), in which a sulfur atom is added to a cysteinyl thiol in a target protein to form a hydropersulfide
Escherichia coli MG1655 was grown in Lysogeny broth (LB) medium, harvested, and resuspended in 50 mM Tris buffer at OD600 nm of 2.0
C58 was cloned into E. coli MG1655 [E. coli (AtBlh)], and recombinant cells rapidly metabolized 200 μM MP to 38.2 ± 2.1 μM sulfide, 55.9 ± 5.7 μM thiosulfate and 10.7 ± 1.5 μM sulfite (Figures 4B–D). These results suggest that GSH can act as a receptor for reactive sulfane sulfur during the mercaptopyruvate sulfurtransferase (MST) reaction to produce GSSH under physiological conditions, and GSSH reacts with small thiols such as GSH to release sulfide

Summary

Introduction

H2S may protect bacterial cells from oxidative stress (Shatalin et al, 2011) and have physiological roles in cellular signaling through protein sulfhydration (Paul and Snyder, 2012; Giedroc, 2017), in which a sulfur atom is added to a cysteinyl thiol in a target protein to form a hydropersulfide (protein-SSH). The Production of H2S and Reactive Sulfane Sulfur elemental sulfur, can react with protein thiols to generate proteinSSH (Toohey, 2011; Ida et al, 2014). There are appreciable amounts (>100 μM) of reactive sulfane sulfur in the plasma, cells, and tissues of mammals (Ida et al, 2014). It is unresolved whether H2S or reactive sulfane sulfur is mainly responsible for protein sulfhydration and resistance to oxidative stress in live cells (Toohey, 2011; Ida et al, 2014)

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