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J. Bacteriol., Dec 1996, 7241-7247, Vol 178, No. 24
E Zientz, S Six and G Unden
In Escherichia coli, two carriers (DcuA and DcuB) for the transport of C4
dicarboxylates in anaerobic growth were known. Here a novel gene dcuC was
identified encoding a secondary carrier (DcuC) for C4 dicarboxylates which
is functional in anaerobic growth. The dcuC gene is located at min 14.1 of
the E. coli map in the counterclockwise orientation. The dcuC gene combines
two open reading frames found in other strains of E. coli K-12. The gene
product (DcuC) is responsible for the transport of C4 dicarboxylates in
DcuA-DcuB-deficient cells. The triple mutant (dcuA dcuB dcuC) is completely
devoid of C4- dicarboxylate transport (exchange and uptake) during
anaerobic growth, and the bacteria are no longer capable of growth by
fumarate respiration. DcuC, however, is not required for C4-dicarboxylate
uptake in aerobic growth. The dcuC gene encodes a putative protein of 461
amino acid residues with properties typical for secondary procaryotic
carriers. DcuC shows sequence similarity to the two major anaerobic C4-
dicarboxylate carriers DcuA and DcuB. Mutants producing only DcuA, DcuB, or
DcuC were prepared. In the mutants, DcuA, DcuB, and DcuC were each able to
operate in the exchange and uptake mode.
Copyright © 1996, American Society for Microbiology
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
Institut fur Mikrobiologie und Weinforschung, Johannes Gutenberg- Universitat Mainz, Federal Republic of Germany.
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