Structural and evolutionary insights into the isoprene monooxygenases.

Area of Science:

• Biogeochemistry
• Microbial Ecology
• Structural Biology

Background:

• Isoprene is a reactive biogenic volatile organic compound (VOC) impacting atmospheric chemistry.
• Microbial degradation pathways for isoprene are not well understood.
• Isoprene monooxygenase (IsoMO) initiates aerobic isoprene degradation.

Purpose of the Study:

• To analyze gene clusters encoding IsoMO in isoprene degraders.
• To reconstruct amino acid phylogenies and generate structural models of IsoMO components.
• To elucidate the structural and evolutionary relationship of IsoMO to other di-iron monooxygenases.

Main Methods:

• Analysis of iso gene clusters from eleven confirmed isoprene degraders.
• Reconstruction of amino acid sequence phylogenies.
• Generation of structural models using AlphaFold2.

Main Results:

• Identified a conserved IsoMO core (IsoA, IsoE, IsoB) with an α₂β₂γ₂ structure.
• The IsoMO core architecture resembles soluble methane monooxygenase (sMMO) hydroxylase.
• IsoA is a conserved subunit and a reliable molecular marker for isoprene degradation.

Conclusions:

• The study presents the first detailed structural model of an IsoMO core.
• IsoMO shares a di-iron catalytic framework with other soluble di-iron monooxygenases, adapted for different substrates.
• Provides a molecular basis for future studies on microbial isoprene turnover and climate change impacts.