The Escherichia coli ynfEFGHI operon encodes polypeptides which are paralogues of dimethyl sulfoxide reductase (DmsABC)

Abstract

The ynfEFGHI operon is a paralogue of the Escherichia coli dmsABC operon. ynfE and ynfF are paralogues of dmsA. ynfG and ynfH are paralogues of dmsB and dmsC, respectively. YnfI ( dmsD) has no dms paralogue. YnfE/F and YnfG could be detected by immunoblotting with anti-DmsAB antibodies when expressed under the control of a tac or dms promoter. Cells harbouring ynfFGH on a multicopy plasmid supported anaerobic growth with dimethyl sulfoxide (DMSO) as respiratory oxidant in a dmsABC deletion, suggesting that YnfFGH forms a heterotimeric enzyme complex similar to DmsABC. Exchange of DmsC by YnfH (DmsAB-YnfH) resulted in membrane localization, anaerobic growth on DMSO, and binding of 2- n-heptyl 4-hydroxyquinoline-N-oxide, indicating that YnfH was a competent anchor. YnfG can also replace DmsB as the electron transfer subunit and assembled [Fe–S] clusters as judged by electron paramagnetic resonance spectroscopy. YnfE and/or YnfF could not form a functional complex with DmsBC and expression of YnfE prevented the accumulation of YnfFGH.