Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The key to the lock that controls nitrogen fixation

04.11.2004


“Bacteria that fix nitrogen only do so when they sense that there is very little nitrogen available in their environment,” says Professor Ray Dixon (Project Leader at the JIC. “Normally the genes for nitrogen fixation are locked off and only unlocked and used when nitrogen levels in the environment fall. We have discovered a key piece of biochemistry that allows us to better understand how the lock operates and so may allow us to alter how it works”.

The bacterium Azotobacter vinelandii is able to fix atmospheric nitrogen when available nitrogen in its environment falls below a threshold level. Nitrogen fixation requires a great deal of energy and so the genes that carry out nitrogen fixation (so called nif genes) are tightly regulated and switched off when not required.

The nif genes are regulated by the action of two proteins, called NifL and NifA. NifA stimulates the activity of nif genes, while NifL normally binds to NifA and renders it inactive. Thus whether the nif genes are active or not depends on the interaction between these two proteins. Both proteins are sensitive to biochemical signals that occur in the bacterial cell when conditions are right for nitrogen fixation. The proteins’ physical shape and structure alters in response to these signals and this affects their ability to bind to one another. The result is that, when conditions are right for nitrogen fixation, NifA is released from the grip of NifL and is then able to stimulate the activity of the nif genes and so switches on nitrogen fixation by the cell.



The latest research has identified a single amino acid change in the NifL protein that prevents the molecule releasing NifA when the appropriate signals are present [2]. This gives the scientists an important clue about the key processes which operate the lock that controls nitrogen fixation.

The discovery will be reported in the international science journal Proceedings of the National Academy of Sciences US, and is available on line in the PNAS Online Early Edition [3].

[1]
The John Innes Centre (JIC), Norwich, UK is an independent, world-leading research centre in plant and microbial sciences. The JIC has over 850 staff and students. JIC carries out high quality fundamental, strategic and applied research to understand how plants and microbes work at the molecular, cellular and genetic levels. The JIC also trains scientists and students, collaborates with many other research laboratories and communicates its science to end-users and the general public. The JIC is grant-aided by the Biotechnology and Biological Sciences Research Council.

[2]
NifA is a sigma factor dependent transcriptional activator that stimulate nif gene activity. Its action is blocked by protein-protein binding with NifL, an anti-activator. NifL is sensitive to the redox and fixed nitrogen status of the cell. Binding of 2-oxoglutarate (an indicator of cell carbon status) to NifA prevents NifL from inhibiting NifA . A critical arginine residue (R306) has been identified in NifL that is required to release NifA under appropriate environmental conditions. Mutation of this residue blocks release of NifA from NifL. The substitution of this arginine significantly alters the conformation of the NifL molecule and inhibits NifA’s response to 2-oxoglutarate. It appears that arginine 306 is critical for coupling the response of NifL to the cellular redox and fixed nitrogen status to a conformational switch that prevents NifL from inhibiting NifA under conditions suitable for nitrogen fixation.

[3]
A crucial arginine residue is required for a conformational switch in NifL to regulate nitrogen fixation in Azotobacter vinelandii. I. Martinez-Argudo, R. Little and R. Dixon. Article #04-05312

Ray Mathias | alfa
Further information:
http://www.bbsrc.ac.uk
http://www.jic.ac.uk

More articles from Life Sciences:

nachricht An ion channel with a doorkeeper: The pH of calcium ions controls ion channel opening
25.06.2019 | Johannes Gutenberg-Universität Mainz

nachricht Symbiotic upcycling: Turning “low value” compounds into biomass
25.06.2019 | Max-Planck-Institut für Marine Mikrobiologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fraunhofer IDMT demonstrates its method for acoustic quality inspection at »Sensor+Test 2019« in Nürnberg

From June 25th to 27th 2019, the Fraunhofer Institute for Digital Media Technology IDMT in Ilmenau (Germany) will be presenting a new solution for acoustic quality inspection allowing contact-free, non-destructive testing of manufactured parts and components. The method which has reached Technology Readiness Level 6 already, is currently being successfully tested in practical use together with a number of industrial partners.

Reducing machine downtime, manufacturing defects, and excessive scrap

Im Focus: Successfully Tested in Praxis: Bidirectional Sensor Technology Optimizes Laser Material Deposition

The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.

Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

For a better climate in the cities: Start-up develops maintenance-free, evergreen moss façades

25.06.2019 | Architecture and Construction

An ion channel with a doorkeeper: The pH of calcium ions controls ion channel opening

25.06.2019 | Life Sciences

Cooling with the sun

25.06.2019 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>