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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)

and

C4-dicarboxylate1 (out) + C4-dicarboxylate2 (in) ⇌

C4-dicarboxylate1 (in) + C4-dicarboxylate2 (out)

This family belongs to the: IT Superfamily.

References associated with 2.A.61 family:

Chen, J., X. Zhu, Z. Tan, H. Xu, J. Tang, D. Xiao, and X. Zhang. (2014). Activating C4-dicarboxylate transporters DcuB and DcuC for improving succinate production. Appl. Microbiol. Biotechnol. 98: 2197-2205. 24323285
Engel, P., R. Krämer, and G. Unden. (1994). Transport of C4-dicarboxylates by anaerobically grown Escherichia coli: energetics and mechanism of exchange, uptake and efflux. Eur. J. Biochem. 222: 605-614. 8020497
Janausch, I.G. and G. Unden. (1999). The dcuD (former yhcL) gene product of escherichia coli as a member of the DcuC family of C4-dicarboxylate carriers: lack of evident expression. Arch. Microbiol. 172: 219-226. 10525738
Six, S., S.C. Andrews, G. Unden, and J.R. Guest. (1994). Escherichia coli possesses two homologous anaerobic C4-dicarboxylate membrane transporters (DcuA and DcuB) distinct from the aerobic dicarboxylate transport system (Dct). J. Bacteriol. 176: 6470-6478. 7961398
Unden, G. and J. Bongaerts. (1997). Alternative respiratory pathways of Escherichia coli: energetics and transcriptional regulation in response to electron acceptors. Biochim. Biophys. Acta 1320: 217-234. 9230919
Zientz, E., I.G. Janausch, S. Six, and G. Unden. (1999). Functioning of DcuC as the C4-dicarboxylate carrier during glucose fermentation by Escherichia coli. J. Bacteriol. 181: 3716-3720. 10368146
Zientz, E., S. Six, and G. Unden. (1996). Identification of a third secondary carrier (DcuC) for anaerobic C4-dicarboxylate transport in Escherichia coli: roles of the three Dcu carriers in uptake and exchange. J. Bacteriol. 178: 7241-7247. 8955408