Plays a role in L-cysteine detoxification. Binds to the dlsT(yhaO)-yhaM operon promoter in the presence but not absence of L-cysteine; activates transcription from the dlsT(yhaO)-yhaM operon. No other DNA target was identified in strain K12 / BW25113. Thiosulfate does not activate its transcription function. Overexpression doubles hydrogen sulfide production in the presence of cysteine. Slightly increased sensitivity to excess L-cysteine, the effect is more pronounced in M9 minimal medium. Loss of expression of dlsT(yhaO)-yhaM operon. Cells no longer produce hydrogen sulfide in the presence of excess cysteine. Extended N-terminus.