The New Role of СysB Transcription Factor in Cysteine Degradation and Production of Hydrogen Sulfide in E. coli
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The paradoxical effect of deletion of the Escherichia coli genes cysK and cysM encoding cysteine synthase enzymes has been studied: such cysteine auxotrophs actively degrade the excess of cysteine transported from the medium to form H2S. We have shown that deletions of any of the known genes controlling the degradation of exogenous cysteine, including the genes aspC, mstA, cysK, cysM, tnaA, metC, and malY, as well as the newly discovered genes yciW, cyuA, cyuP, and cyuR, do not deprive the cysteine auxotrophs ΔcysK ΔcysM of the ability to degrade cysteine. Cysteine degradation in the ΔcysK ΔcysM mutant is positively regulated by the products of the cysB and cysE genes. It is significant that the ΔcysK ΔcysM mutant shows an increased transcription of the genes opposing the oxidative stress (sodA, catG, arcA, and cydD). We assume that oxidative stress in cells of the ΔcysK ΔcysM mutant is provoked by restriction of cysteine resynthesis, while cysB-dependent degradation of exogenous cysteine and generated H2S provide protection against oxidative stress.
Keywords:hydrogen sulfide production degradation and transport of cysteine CysB regulon oxidative stress E. coli
We are grateful to E.A. Nudler for valuable comments in discussing the results of this work.
The results of the studies presented in Figs. 2 and 3 were obtained in the framework of the Program of Fundamental Research of the State Academies of Sciences for 2013–2020 (topic no. 01201363822). The results of the studies presented in Figs. 4–8 were obtained using funds of the Russian Science Foundation (project no. 17-74-30030).
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