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.

Autor: Schubert C; Microbiology and Wine Research, Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany., Zedler S; Microbiology and Wine Research, Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany., Strecker A; Microbiology and Wine Research, Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany., Unden G; Microbiology and Wine Research, Institute for Molecular Physiology, Johannes Gutenberg-University Mainz, Mainz, Germany.
Jazyk: angličtina
Zdroj: Molecular microbiology [Mol Microbiol] 2021 Apr; Vol. 115 (4), pp. 526-538. Date of Electronic Publication: 2020 Nov 03.
DOI: 10.1111/mmi.14620
Abstrakt: 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 metabolism, GlnB. GlnB interacted with AspA and stimulated its L-aspartate deaminase activity (NH 3 -forming), but not the reverse amination reaction. GlnB stimulation required 2-oxoglutarate and ATP, or uridylylated GlnB-UMP, consistent with the activation of nitrogen assimilation under nitrogen limitation. Binding to AspA was lost in the GlnB(Y51F) mutant of the uridylylation site. AspA, therefore, represents a new type of GlnB target that binds GlnB (with ATP and 2-oxoglutarate), or GlnB-UMP (with or without effectors), and both situations stimulate AspA deamination activity. Thus, AspA represents the central enzyme for nitrogen assimilation from L-aspartate, and AspA is integrated into the nitrogen assimilation network by the regulator GlnB.
(© 2020 John Wiley & Sons Ltd.)
Databáze: MEDLINE
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