2.A.61 The C4-dicarboxylate Uptake C (DcuC) Family
A single functionally characterized protein comprises the DcuC family. This is an anaerobic C4-dicarboxylate transporter (DcuC) of E. coli. A paralogue is encoded on the E. coli genome (455 amino acyl residues; 10 putative TMSs; spP45428), and a homologue is probably present in Haemophilus influenzae. The latter is included in the SwissProt database as two distinct but adjacent ORFs, HI0586 (145 aas; 4 putative TMSs; spP44019) and HI0585 (279 aas; 6 putative TMSs; spP44018). These two putative ORFs may be the N- and C-terminal parts of a single protein, respectively.
The DcuC protein is induced only under anaerobic conditions and is not repressed by glucose. It may therefore function as a succinate efflux system during anaerobic glucose fermentation. However, when overexpressed, it can replace either DcuA or DcuB in catalyzing fumarate-succinate exchange and fumarate uptake.
The reactions probably catalyzed by the E. coli DcuC protein are:
C4-dicarboxylate (out) + nH+ (out) → C4-dicarboxylate (in) + nH+ (in)
C4-dicarboxylate1 (out) + C4-dicarboxylate2 (in) ⇌
C4-dicarboxylate1 (in) + C4-dicarboxylate2 (out).