Premium
DcuA of aerobically grown Escherichia coli serves as a nitrogen shuttle (L‐aspartate/fumarate) for nitrogen uptake
Author(s) -
Strecker Alexander,
Schubert Christopher,
Zedler Sandra,
Steinmetz Philipp,
Unden Gottfried
Publication year - 2018
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14074
Subject(s) - biochemistry , biology , antiporter , escherichia coli , nitrogen , metabolism , anaerobic exercise , transporter , chemistry , membrane , organic chemistry , gene , physiology
Summary DcuA of Escherichia coli is known as an alternative C 4 ‐dicarboxylate transporter for the main anaerobic C 4 ‐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 C 4 ‐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 C 4 ‐dicarboxylate uptake (like DctA), or an L‐aspartate/C 4 ‐dicarboxylate antiport (unlike DctA). DcuA preferred L‐aspartate to succinate in transport ( K M = 43 and 844 µM, respectively), whereas DctA has higher affinity for C 4 ‐dicarboxylates like succinate compared to L‐aspartate. When L‐aspartate was supplied as the sole nitrogen source together with glycerol as the carbon source, L‐aspartate was taken up by the bacteria and fumarate (or L‐malate) was excreted in equimolar amounts. Both reactions depended on DcuA. L‐Aspartate was taken up in amounts required for nitrogen metabolism but not for carbon metabolism. Therefore, DcuA catalyzes an L‐aspartate/C 4 ‐dicarboxylate antiport serving as a nitrogen shuttle for nitrogen supply without net carbon supply.