0000000000403266
AUTHOR
Sandra Zedler
A Na+-coupled C4-dicarboxylate transporter (Asuc_0304) and aerobic growth of Actinobacillus succinogenes on C4-dicarboxylates
Actinobacillus succinogenes, which is known to produce large amounts of succinate during fermentation of hexoses, was able to grow on C4-dicarboxylates such as fumarate under aerobic and anaerobic conditions. Anaerobic growth on fumarate was stimulated by glycerol and the major product was succinate, indicating the involvement of fumarate respiration similar to succinate production from glucose. The aerobic growth on C4-dicarboxylates and the transport proteins involved were studied. Fumarate was oxidized to acetate. The genome of A. succinogenes encodes six proteins with similarity to secondary C4-dicarboxylate transporters, including transporters of the Dcu (C4-dicarboxylate uptake), Dcu…
L‐Aspartate as a high‐quality nitrogen source in Escherichia coli : Regulation of L‐aspartase by the nitrogen regulatory system and interaction of L‐aspartase with GlnB
Escherichia coli uses the C4-dicarboxylate transporter DcuA for L-aspartate/fumarate antiport, which results in the exploitation of L-aspartate for fumarate respiration under anaerobic conditions and for nitrogen assimilation under aerobic and anaerobic conditions. L-Aspartate represents a high-quality nitrogen source for assimilation. Nitrogen assimilation from L-aspartate required DcuA, and aspartase AspA to release ammonia. Ammonia is able to provide by established pathways the complete set of intracellular precursors (ammonia, L-aspartate, L-glutamate, and L-glutamine) for synthesizing amino acids, nucleotides, and amino sugars. AspA was regulated by a central regulator of nitrogen meta…
DcuA of aerobically grownEscherichia coliserves as a nitrogen shuttle (L‐aspartate/fumarate) for nitrogen uptake
DcuA of Escherichia coli is known as an alternative C4 -dicarboxylate transporter for the main anaerobic C4 -dicarboxylate transporter DcuB. Since dcuA is expressed constitutively under aerobic and anaerobic conditions, DcuA was suggested to serve aerobically as a backup for the aerobic (DctA) transporter, or for the anabolic uptake of C4 -dicarboxylates. In this work, it is shown that DcuA is required for aerobic growth with L-aspartate as a nitrogen source, whereas for growth with L-aspartate as a carbon source, DctA was needed. Strains with DcuA catalyzed L-aspartate and C4 -dicarboxylate uptake (like DctA), or an L-aspartate/C4 -dicarboxylate antiport (unlike DctA). DcuA preferred L-asp…