Model Calculations Suggest that the Central Carbon in the FeMo-Cofactor of Nitrogenase Becomes Protonated in the Process of Nitrogen Fixation

2016 ◽  
Vol 138 (33) ◽  
pp. 10485-10495 ◽  
Author(s):  
Per E. M. Siegbahn
Keyword(s):  
Nitrogen Fixation ◽  
Model Calculations ◽  
Central Carbon ◽  
Femo Cofactor

scholarly journals Metal trafficking for nitrogen fixation: NifQ donates molybdenum to NifEN/NifH for the biosynthesis of the nitrogenase FeMo-cofactor

2008 ◽  
Vol 105 (33) ◽  
pp. 11679-11684 ◽  
Author(s):  
J. A. Hernandez ◽  
L. Curatti ◽  
C. P. Aznar ◽  
Z. Perova ◽  
R. D. Britt ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Metal Trafficking ◽  
Femo Cofactor

scholarly journals Genome-Wide Analyses of Proteome and Acetylome in Zymomonas mobilis Under N2-Fixing Condition

2021 ◽  
Vol 12 ◽  
Author(s):  
Ayesha Nisar ◽  
Xiangxu Gongye ◽  
Yuhuan Huang ◽  
Sawar Khan ◽  
Mao Chen ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Carbon Metabolism ◽  
Zymomonas Mobilis ◽  
Protein Biosynthesis ◽  
Central Carbon Metabolism ◽  
Biofuel Production ◽  
Ammonia Assimilation ◽  
Protein Acetylation ◽  
High Throughput Analysis ◽  
Central Carbon

Zymomonas mobilis, a promising candidate for industrial biofuel production, is capable of nitrogen fixation naturally without hindering ethanol production. However, little is known about the regulation of nitrogen fixation in Z. mobilis. We herein conducted a high throughput analysis of proteome and protein acetylation in Z. mobilis under N2-fixing conditions and established its first acetylome. The upregulated proteins mainly belong to processes of nitrogen fixation, motility, chemotaxis, flagellar assembly, energy production, transportation, and oxidation–reduction. Whereas, downregulated proteins are mainly related to energy-consuming and biosynthetic processes. Our acetylome analyses revealed 197 uniquely acetylated proteins, belonging to major pathways such as nitrogen fixation, central carbon metabolism, ammonia assimilation pathway, protein biosynthesis, and amino acid metabolism. Further, we observed acetylation in glycolytic enzymes of central carbon metabolism, the nitrogenase complex, the master regulator NifA, and the enzyme in GS/GOGAT cycle. These findings suggest that protein acetylation may play an important role in regulating various aspects of N2-metabolism in Z. mobilis. This study provides new knowledge of specific proteins and their associated cellular processes and pathways that may be regulated by protein acetylation in Z. mobilis.

scholarly journals Characterization of Mutations That Affect the Nonoxidative Pentose Phosphate Pathway in Sinorhizobium meliloti

2017 ◽  
Vol 200 (2) ◽  
Author(s):  
Justin P. Hawkins ◽  
Patricia A. Ordonez ◽  
Ivan J. Oresnik
Keyword(s):  
Nitrogen Fixation ◽  
Mutant Strain ◽  
Pentose Phosphate Pathway ◽  
Carbon Metabolism ◽  
Sinorhizobium Meliloti ◽  
Iron Acquisition ◽  
Central Carbon Metabolism ◽  
Pentose Phosphate ◽  
Content Type ◽  
Central Carbon

ABSTRACTSinorhizobium melilotiis a Gram-negative alphaproteobacterium that can enter into a symbiotic relationship withMedicago sativaandMedicago truncatula. Previous work determined that a mutation in thetkt2gene, which encodes a putative transketolase, could prevent medium acidification associated with a mutant strain unable to metabolize galactose. Since the pentose phosphate pathway inS. melilotiis not well studied, strains carrying mutations in eithertkt2andtal, which encodes a putative transaldolase, were characterized. Carbon metabolism phenotypes revealed that both mutants were impaired in growth on erythritol and ribose. This phenotype was more pronounced for thetkt2mutant strain, which also displayed auxotrophy for aromatic amino acids. Changes in pentose phosphate pathway metabolite concentrations were also consistent with a mutation in eithertkt2ortal. The concentrations of metabolites in central carbon metabolism were also found to shift dramatically in strains carrying atkt2mutation. While the concentrations of proteins involved in central carbon metabolism did not change significantly under any conditions, the levels of those associated with iron acquisition increased in the wild-type strain with erythritol induction. These proteins were not detected in either mutant, resulting in less observable rhizobactin production in thetkt2mutant. While both mutants were impaired in succinoglycan synthesis, only thetkt2mutant strain was unable to establish symbiosis with alfalfa. These results suggest thattkt2andtalplay central roles in regulating the carbon flow necessary for carbon metabolism and the establishment of symbiosis.IMPORTANCESinorhizobium melilotiis a model organism for the study of plant-microbe interactions and metabolism, especially because it effects nitrogen fixation. The ability to derive the energy necessary for nitrogen fixation is dependent on an organism's ability to metabolize carbon efficiently. The pentose phosphate pathway is central in the interconversion of hexoses and pentoses. This study characterizes the key enzymes of the nonoxidative branch of the pentose phosphate pathway by using defined genetic mutations and shows the effects the mutations have on the metabolite profile and on physiological processes such as the biosynthesis of exopolysaccharide, as well as the ability to regulate iron acquisition.

Effects of Ambipolar Diffusion on Prominence Thread Models

1994 ◽  
Vol 144 ◽  
pp. 315-321 ◽  
Author(s):  
M. G. Rovira ◽  
J. M. Fontenla ◽  
J.-C. Vial ◽  
P. Gouttebroze
Keyword(s):  
Energy Balance ◽  
Transition Region ◽  
Ambipolar Diffusion ◽  
Line Profiles ◽  
Balance Equations ◽  
Model Calculations ◽  
Partial Frequency ◽  
Frequency Redistribution ◽  
Partial Frequency Redistribution ◽  
Theoretical Structure

AbstractWe have improved previous model calculations of the prominence-corona transition region including the effect of the ambipolar diffusion in the statistical equilibrium and energy balance equations. We show its influence on the different parameters that characterize the resulting prominence theoretical structure. We take into account the effect of the partial frequency redistribution (PRD) in the line profiles and total intensities calculations.

Influence of stable iodine on the uptake of the thyroid – model vs. experiment

2001 ◽  
Vol 40 (01) ◽  
pp. 31-37 ◽  
Author(s):  
U. Wellner ◽  
E. Voth ◽  
H. Schicha ◽  
K. Weber
Keyword(s):  
Time Course ◽  
Compartment Model ◽  
The Body ◽  
Iodine Uptake ◽  
Model Calculations ◽  
Physiological Conditions ◽  
Iodine Supply ◽  
Predicted Values ◽  
The Individual ◽  
Stable Iodine

Summary Aim: The influence of physiological and pharmacological amounts of iodine on the uptake of radioiodine in the thyroid was examined in a 4-compartment model. This model allows equations to be derived describing the distribution of tracer iodine as a function of time. The aim of the study was to compare the predictions of the model with experimental data. Methods: Five euthyroid persons received stable iodine (200 μg, 10 mg). 1-123-uptake into the thyroid was measured with the Nal (Tl)-detector of a body counter under physiological conditions and after application of each dose of additional iodine. Actual measurements and predicted values were compared, taking into account the individual iodine supply as estimated from the thyroid uptake under physiological conditions and data from the literature. Results: Thyroid iodine uptake decreased from 80% under physiological conditions to 50% in individuals with very low iodine supply (15 μg/d) (n = 2). The uptake calculated from the model was 36%. Iodine uptake into the thyroid did not decrease in individuals with typical iodine supply, i.e. for Cologne 65-85 μg/d (n = 3). After application of 10 mg of stable iodine, uptake into the thyroid decreased in all individuals to about 5%, in accordance with the model calculations. Conclusion: Comparison of theoretical predictions with the measured values demonstrated that the model tested is well suited for describing the time course of iodine distribution and uptake within the body. It can now be used to study aspects of iodine metabolism relevant to the pharmacological administration of iodine which cannot be investigated experimentally in humans for ethical and technical reasons.

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