RT Journal Article
SR Electronic
T1 GlnK facilitates the dynamic regulation of bacterial nitrogen assimilation
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 127662
DO 10.1101/127662
A1 Adam Gosztolai
A1 Jörg Schumacher
A1 Volker Behrends
A1 Jacob G Bundy
A1 Franziska Heydenreich
A1 Mark H Bennett
A1 Martin Buck
A1 Mauricio Barahona
YR 2017
UL http://biorxiv.org/content/early/2017/04/15/127662.abstract
AB Ammonium assimilation in E. coli is regulated by two paralogous proteins (GlnB and GlnK), which orchestrate interactions with regulators of gene expression, transport proteins and metabolic pathways. Yet how they conjointly modulate the activity of glutamine synthetase (GS), the key enzyme for nitrogen assimilation, is poorly understood. We combine experiments and theory to study the dynamic roles of GlnB and GlnK during nitrogen starvation and upshift. We measure time-resolved in vivo concentrations of metabolites, total and post-translationally modified proteins, and develop a concise biochemical model of GlnB and GlnK that incorporates competition for active and allosteric sites, as well as functional sequestration of GlnK. The model predicts the responses of GS, GlnB and GlnK under time-varying external ammonium level in the wild type and two genetic knock-outs. Our results show that GlnK is tightly regulated under nitrogen-rich conditions, yet it is expressed during ammonium run-out and starvation. This suggests a role for GlnK as a buffer of nitrogen shock after starvation, and provides a further functional link between nitrogen and carbon metabolisms.