Calm on the surface, dynamic on the inside. Molecular homeostasis of Anabaena sp. PCC 7120 nitrogen metabolism

Abstract

Nitrogen sources are all converted into ammonium/ia as a first step of assimilation. It is reasonable to expect that molecular components involved in the transport of ammonium/ ia across biological membranes connect with the regulation of both nitrogen and central metabolism. We applied both genetic (i.e., Δamt mutation) and environmental treatments to a target biological system, the cyanobacterium Anabaena sp PCC 7120. The aim was to both perturb nitrogen metabolism and induce multiple inner nitrogen states, respectively, followed by targeted quantification of key proteins, metabolites and enzyme activities. The absence of AMT transporters triggered a substantial whole-system response, affecting enzyme activities and quantity of proteins and metabolites, spanning nitrogen and carbon metabolisms. Moreover, the Δamt strain displayed a molecular fingerprint indicating nitrogen deficiency even under nitrogen replete conditions. Contrasting with such dynamic adaptations was the striking near-complete lack of an externally measurable altered phenotype. We conclude that this species evolved a highly robust and adaptable molecular network to maintain homeostasis, resulting in substantial internal but minimal external perturbations. This analysis provides evidence for a potential role of AMT transporters in the regulatory/signalling network of nitrogen metabolism and the existence of a novel fourth regulatory mechanism controlling glutamine synthetase activity.

Transcriptomic and photosynthetic analyses of Synechocystis sp. PCC6803 and Chlorogloeopsis fritschii sp. PCC6912 exposed to an M-dwarf spectrum under an anoxic atmosphere

“…Interestingly, the key enzyme of N assimilation, glutamine synthetase (GS, encoded by glnA gene), which catalyzes the reaction that converts glutamate to glutamine ( Klähn et al., 2018 ), was not differentially regulated at significant levels in any condition tested. The inhibition of GS indeed takes place at the post-translational level, through the inhibitory factors IF7 and IF17, encoded respectively by the genes gifA and gifB ( Klähn et al., 2018 ; Perin et al., 2021 ). The upregulation of norB instead is not clear.…”

Dyskeratosis Congenita Links Telomere Attrition to 
Age-Related Systemic Energetics

“…The samples were analyzed by ion-pairing chromatography/mass spectrometry, as described fully in ( 33 ), with additional transitions added for the SIL standards, as listed in ( 34 ), using a XEVO TQ-S tandem mass spectrometer coupled to an Acquity ultraperformance liquid chromatography (UPLC) binary solvent manager equipped with a CTC autosampler (Waters Ltd, Wilmslow, UK). Briefly, data were acquired with electrospray ionization in negative mode, and the chromatography used a Waters HSS T3 column (1.8 µm, 2.1 × 100 mm) with a binary solvent system of 10 mM tributylamine + 15 mM acetic acid in water (solvent A), and 80% methanol + 20% isopropanol (solvent B) to 100%.…”

Telomerase deficiency in humans is associated with systemic age-related changes in energy metabolism

“…Compound specific mass spectrometry parameters were determined individually and described in (Perin et al, 2021); two transitions were monitored for each analyte to confirm its identity where possible. The raw LC-MS data were analyzed using Skyline (MacCoss Lab, (Pino et al, 2020).…”