NosL is necessary for the assembly of the active site of the Cu2S cluster

The new research reveals how soil bacteria build the only known enzyme to destroy the powerful global warming and ozone-depleting gas nitrous oxide. In addition to carbon dioxide (CO2) and methane, the greenhouse gas nitrous oxide (N2O), commonly known as "laughing gas", has attracted great attention, and the international community is paying attention to reducing emissions. It is hoped that these findings will help pave the way for strategies to mitigate the destructive impact of N2O.

In addition to carbon dioxide (CO2) and methane, the greenhouse gas nitrous oxide (N2O), commonly known as "laughing gas", has attracted great attention, and the international community is paying attention to reducing emissions.

This discovery, published today in the journal Chemical Science, is expected to pave the way for strategies to mitigate the destructive effects of this gas that causes climate change.

The global warming potential value of nitrous oxide is about 300 times that of carbon dioxide, and it stays in the atmosphere for about 120 years, accounting for about 9% of the total greenhouse gases.

It will also destroy the ozone layer, and its effect is similar to that of chlorofluorocarbons (cfcs) which are now banned.

In order to meet the demand of the growing global population for food supply, the synthetic nitrogen fertilizer added to agricultural soil is decomposed by microorganisms, and the content of N2O in the atmosphere is increasing year by year.

Professor Nick Lebron of the School of Chemistry at the University of East Anglia said: "It is well known that some bacteria can 'breathe' N2O in an environment with limited oxygen."

"This ability completely depends on an enzyme called 'nitrous oxide reductase', which is the only enzyme known to destroy N2O. Therefore, it is very important to control the level of this gas that causes climate change.

"We want to know more about how soil bacteria use this enzyme to destroy nitrous oxide."

The N2O-consuming part of the enzyme (called "active site") is unique in biology and consists of a complex arrangement of copper and sulfur (Cu2S cluster). So far, there is still a lack of knowledge about how bacteria establish this unusual active site.

The research team of the University of East Anglia has found a protein called NosL, which is necessary for the assembly of the active site of the Cu2S cluster and makes the enzyme active.

They found that bacteria lacking NosL still produce this enzyme, but it contains less copper sulfide active sites. In addition, when the same bacteria grow under the condition of insufficient Cu2S supply, there is no active site in the enzyme.

The team also showed that NosL is a copper-binding protein, which indicates that it directly provides copper for the assembly of the active sites of the copper-sulfide cluster.

Professor Le Brun said: "The discovery of the function of NosL is the first step to understand how the unique active site of nitrous oxide reductase is assembled. This is the key information, because when the assembly is wrong, the active enzyme will cause N2O to be released into the atmosphere."

The team is led by Professor Nick Lebron and Dr. Andy Gates of the School of Biological Sciences of the University of East Anglia, including Professor David Richardson, Vice President of the University of East Anglia, who is also from the School of Biological Sciences. They are part of the international network of the European Union, focusing on understanding the different aspects of N2O and nitrogen cycle.

Dr. Gates said: "The society is generally aware of the need to solve carbon dioxide emissions, but nitrous oxide is now becoming an urgent global problem, requiring researchers with different skills to work together to prevent the further destructive effects of climate change."

"With the increasing understanding of the enzymes that produce and destroy N2O, we are closer and closer to formulating strategies to mitigate the destructive impact of this gas that causes climate change on the Earth's environment."

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