Fumarate Regulation of Gene Expression in Escherichia coli by the DcuSR ( dcuSR Genes) Two-Component Regulatory System

Abstract

ABSTRACT In Escherichia coli the genes encoding the anaerobic fumarate respiratory system are transcriptionally regulated by C 4 -dicarboxylates. The regulation is effected by a two-component regulatory system, DcuSR, consisting of a sensory histidine kinase (DcuS) and a response regulator (DcuR). DcuS and DcuR are encoded by the dcuSR genes (previously yjdHG ) at 93.7 min on the calculated E. coli map. Inactivation of the dcuR and dcuS genes caused the loss of C 4 -dicarboxylate-stimulated synthesis of fumarate reductase ( frdABCD genes) and of the anaerobic fumarate-succinate antiporter DcuB ( dcuB gene). DcuS is predicted to contain a large periplasmic domain as the supposed site for C 4 -dicarboxylate sensing. Regulation by DcuR and DcuS responded to the presence of the C 4 -dicarboxylates fumarate, succinate, malate, aspartate, tartrate, and maleate. Since maleate is not taken up by the bacteria under these conditions, the carboxylates presumably act from without. Genes of the aerobic C 4 -dicarboxylate pathway encoding succinate dehydrogenase ( sdhCDAB ) and the aerobic succinate carrier ( dctA ) are only marginally or negatively regulated by the DcuSR system. The CitAB two-component regulatory system, which is highly similar to DcuSR, had no effect on C 4 -dicarboxylate regulation of any of the genes.