Science: Revealing how methane-oxidizing bacteria convert methane into fuel

March 19, 2022 / Bio Valley BIOON / -- methanotrophic bacteria consume 30 million metric tons of methane each year and are attracted by their natural ability to convert this powerful greenhouse gas into usable fuel scientists

In a new study, researchers from Northwestern University discovered the key structures that drive the process by studying the enzymes that methane-oxidizing bacteria use to catalyze this complex reaction

"Methane has strong chemical bonds, so having an enzyme that can break its bonds is quite remarkable," said Amy Rosenzweig of Northwestern University, corresponding author of the paper

The enzyme, called particulate methane monooxygenase (pMMO), is a particularly difficult protein to study because it is embedded in the cell membranes of methane-oxidizing bacteria

Cryo-electron microscopy revealed a never-before-seen structure of the protein pMMO in membranes.

In this new study, the authors used a completely new technique

"By recreating the enzyme's natural environment within the nanodisc, we were able to restore its activity," Koo said.

These authors used cryo-electron microscopy (cryo-EM), a technique well suited for membrane proteins because the lipid membrane environment was not disturbed throughout the experiment

"As a result of the recent 'revolution in cryo-EM', we were able to observe structural details at the atomic level," Rosenzweig said.

Rosenzweig said the enzyme's cryo-EM structure provides a new starting point for answering questions that continue to pile up: How does methane get into the enzyme's active site? Or how is methanol released from this enzyme? How does the copper in the active site react chemically? Next, the authors plan to study the enzyme directly inside methane-oxidizing bacteria cells using a cutting-edge imaging technique called cryo-electron tomography (cryo-ET)

If successful, the authors will be able to observe exactly how the enzyme is arranged in cell membranes, determine how it operates in its true natural environment, and learn whether other proteins surrounding the enzyme interact with it

"If you want to optimize the enzyme, insert it into biological manufacturing pathways, or consume pollutants other than methane, then we need to know what it looks like in the natural environment and where the methane binds," Rosenzweig said

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Christopher W.