Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


The key to the lock that controls nitrogen fixation


“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].

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.

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.

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:

More articles from Life Sciences:

nachricht Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München

nachricht Second research flight into zero gravity
21.10.2016 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Novel mechanisms of action discovered for the skin cancer medication Imiquimod

21.10.2016 | Life Sciences

Second research flight into zero gravity

21.10.2016 | Life Sciences

How Does Friendly Fire Happen in the Pancreas?

21.10.2016 | Life Sciences

More VideoLinks >>>