Dataset Information

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

ABSTRACT: 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.

SUBMITTER: Spinola-Amilibia M

PROVIDER: S-EPMC10511194 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature

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

Spínola-Amilibia Mercedes M Illanes-Vicioso Ramiro R Ruiz-López Elena E Colomer-Vidal Pere P Rodriguez-Ventura Francisco F Peces Pérez Rosa R Arias Clemente F CF Torroba Tomas T Solà Maria M Arias-Palomo Ernesto E Bertocchini Federica F

Science advances 20230920 38

Plastic waste management is a pressing ecological, social, and economic challenge. The saliva of the lepidopteran <i>Galleria mellonella</i> larvae is capable of oxidizing and depolymerizing polyethylene in hours at room temperature. Here, we analyze by cryo-electron microscopy (cryo-EM) <i>G. mellonella</i>'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/phenoloxida ...[more]

PMID: 37729416

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Project description:We have used x-ray crystallography to determine the structures of sperm whale myoglobin (Mb) in four different ligation states (unligated, ferric aquomet, oxygenated, and carbonmonoxygenated) to a resolution of better than 1.2 A. Data collection and analysis were performed in as much the same way as possible to reduce model bias in differences between structures. The structural differences among the ligation states are much smaller than previously estimated, with differences of <0.25 A root-mean-square deviation among all atoms. One structural parameter previously thought to vary among the ligation states, the proximal histidine (His-93) azimuthal angle, is nearly identical in all the ferrous complexes, although the tilt of the proximal histidine is different in the unligated form. There are significant differences, however, in the heme geometry, in the position of the heme in the pocket, and in the distal histidine (His-64) conformations. In the CO complex the majority conformation of ligand is at an angle of 18 +/- 3 degrees with respect to the heme plane, with a geometry similar to that seen in encumbered model compounds; this angle is significantly smaller than reported previously by crystallographic studies on monoclinic Mb crystals, but still significantly larger than observed by photoselection. The distal histidine in unligated Mb and in the dioxygenated complex is best described as having two conformations. Two similar conformations are observed in MbCO, in addition to another conformation that has been seen previously in low-pH structures where His-64 is doubly protonated. We suggest that these conformations of the distal histidine correspond to the different conformational substates of MbCO and MbO(2) seen in vibrational spectra. Full-matrix refinement provides uncertainty estimates of important structural parameters. Anisotropic refinement yields information about correlated disorder of atoms; we find that the proximal (F) helix and heme move approximately as rigid bodies, but that the distal (E) helix does not.

Dataset Information

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

Publications

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

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