 An anaerobic C4-dicarboxylate transporter (DcuC) of "E. coli" (TC# 2.A.61.1.1) has 14 putative transmembrane regions, is induced only under anaerobic conditions, and is not repressed by glucose.DcuC may therefore function as a succinate efflux system during anaerobic glucose fermentation.However, when overexpressed, it can replace either DcuA or DcuB in catalysing fumarate-succinate exchange and fumarate uptake.