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Plastic degradation by insect hexamerins: Near-atomic resolution structures of the polyethylene-degrading proteins from the wax worm saliva

Science Advances 2023 34 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Mercedes Spínola‐Amilibia, R. Illanes, Elena Ruiz-López, Pere Colomer-Vidal, Francisco Rodríguez-Ventura, Rosa Peces Pérez, Clemente F. Arias, Tomás Torroba, Marı́a Solà, Ernesto Arias‐Palomo, Federica Bertocchini

Summary

Researchers used cryo-electron microscopy to analyze the saliva of wax worm larvae and identified four hexamerin proteins capable of oxidizing and breaking down polyethylene plastic at room temperature. The study provides near-atomic resolution structures of these proteins, including a newly identified factor called Cora, offering insights that could advance biological approaches to plastic waste management.

Polymers
Study Type In vivo

Plastic waste management is a pressing ecological, social, and economic challenge. The saliva of the lepidopteran Galleria mellonella larvae is capable of oxidizing and depolymerizing polyethylene in hours at room temperature. Here, we analyze by cryo-electron microscopy (cryo-EM) G. mellonella's saliva directly from the native source. The three-dimensional reconstructions reveal that the buccal secretion is mainly composed of four hexamerins belonging to the hemocyanin/phenoloxidase family, renamed Demetra, Cibeles, Ceres, and a previously unidentified factor termed Cora. Functional assays show that this factor, as its counterparts Demetra and Ceres, is also able to oxidize and degrade polyethylene. The cryo-EM data and the x-ray analysis from purified fractions show that they self-assemble primarily into three macromolecular complexes with striking structural differences that likely modulate their activity. Overall, these results establish the ground to further explore the hexamerins' functionalities, their role in vivo, and their eventual biotechnological application.

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