Conserved leucine-rich repeat proteins in the adhesive projectile slime of velvet worms

Proceedings of the National Academy of Sciences · 2025-03-18 · 1 citations

The slime of velvet worms (Onychophora) is a protein-based bioadhesive that undergoes rapid, yet reversible transition from a fluid into stiff fibers used for prey capture and defense, but the mechanism by which this phase transition functions is largely unknown. Here, integrating transcriptomic and proteomic approaches with AI-guided structure predictions, we discover a group of evolutionarily conserved leucine-rich repeat (LRR) proteins in velvet worm slime that readily adopt a receptor-like, protein-binding "horseshoe" structure. Our structural predictions suggest dimerization of LRR proteins and support their interactions with conserved β-sheet-rich domains of high-molecular-weight proteins, the primary building blocks of velvet worm slime fibers. This suggests that LRR proteins might be involved in reversible, receptor-based supramolecular interactions in these biofibers, providing potential avenues for fabricating fully recyclable (bio)polymeric materials.

Receptor-based protein binding in the supramolecular network of velvet worm slime

bioRxiv (Cold Spring Harbor Laboratory) · 2024-10-28

Abstract The slime of velvet worms (Onychophora) is a protein-based bioadhesive that undergoes rapid, yet reversible transition from a fluid into stiff fibers used for prey capture and defense, but the mechanism by which this phase transition functions is largely unknown. Here, integrating transcriptomic and proteomic approaches with AI-guided structure predictions, we discover a group of evolutionarily conserved leucine-rich repeat (LRR) proteins in velvet worm slime that readily adopt a receptor-like, protein-binding “horseshoe” structure. Our structural predictions suggest dimerization of LRR proteins and support their interactions with conserved β-sheets-rich domains of high-molecular-weight proteins, the primary building blocks of velvet worm slime fibers. This previously unknown functional context of LRR proteins is presumably involved in reversible, receptor-based supramolecular network formation in these adhesive biofibers and provides possible new avenues for fabricating fully recyclable (bio)polymeric materials. Significance Statement Analyzing structure-function-relationships underlying reversible fiber formation in velvet worm slime may inspire avenues for the sustainable fabrication of protein-based polymeric materials. Here, we present evidence for an evolutionarily conserved mechanism of reversible fiber formation in velvet worm slime based on the receptor-like binding of fiber forming proteins by a leucine-rich repeat (LRR) protein. The structures of both protein components are highly conserved evolutionarily in the two distantly related velvet worm subgroups, indicating pervasive presence of this mechanism across species that has been maintained through the last ∼380 MY. Our results suggest that the ubiquitously occurring LRR motif—better known for its innate immunity and developmental roles—has a novel identified function in processing a biological material, which might contribute to the development of sustainable bio-inspired materials.

The Internal Structure of the Velvet Worm Projectile Slime: A Small‐Angle Scattering Study

Small · 2023-02-24 · 6 citations

For prey capture and defense, velvet worms eject an adhesive slime which has been established as a model system for recyclable complex liquids. Triggered by mechanical agitation, the liquid bio-adhesive rapidly transitions into solid fibers. In order to understand this mechanoresponsive behavior, here, the nanostructural organization of slime components are studied using small-angle scattering with neutrons and X-rays. The scattering intensities are successfully described with a three-component model accounting for proteins of two dominant molecular weight fractions and nanoscale globules. In contrast to the previous assumption that high molecular weight proteins-the presumed building blocks of the fiber core-are contained in the nanoglobules, it is found that the majority of slime proteins exist freely in solution. Only less than 10% of the slime proteins are contained in the nanoglobules, necessitating a reassessment of their function in fiber formation. Comparing scattering data of slime re-hydrated with light and heavy water reveals that the majority of lipids in slime are contained in the nanoglobules with homogeneous distribution. Vibrating mechanical impact under exclusion of air neither leads to formation of fibers nor alters the bulk structure of slime significantly, suggesting that interfacial phenomena and directional shearing are required for fiber formation.

Phosphonated glycans as post-translational modifications of proteins in velvet worm slime

ChemRxiv · 2023-03-17

To capture prey, onychophorans (velvet worms) expel a slime that forms stiff fibers upon shearing and dehydration. The high quantities of phosphorus previously found in the slime of the velvet worm Euperipatoides rowelli were ascribed to protein phosphorylation. We provide clear evidence, instead, that it is primarily present as phosphonate moieties in the slime of representative from both major onychophoran subgroups which diverged ~380 MYA. Advanced NMR and mass spectrometry demonstrate that 2-aminoethyl phosphonate (2-AEP) is associated with high molecular weight slime proteins as phosphonoglycans. Biogenic phosphonates are a substantial component of the organophosphorus cycle in marine environments but were not previously reported in terrestrial invertebrates. The evolutionary conservation of this rare protein modification suggests a potential role in the formation and function of these biological adhesive fibers with implications for bio-inspiration.

The Toxicology Investigators Consortium 2022 Annual Report

Journal of Medical Toxicology · 2023 · 16 citations

• Medicine
• Emergency medicine
• Family medicine

Peculiar Phosphonate Modifications of Velvet Worm Slime Revealed by Advanced Nuclear Magnetic Resonance and Mass Spectrometry

Journal of the American Chemical Society · 2023 · 15 citations

• Chemistry
• Biochemistry
• Chromatography

Nature is rich with examples of highly specialized biological materials produced by organisms for functions, including defense, hunting, and protection. Along these lines, velvet worms (Onychophora) expel a protein-based slime used for hunting and defense that upon shearing and dehydration forms fibers as stiff as thermoplastics. These fibers can dissolve back into their precursor proteins in water, after which they can be drawn into new fibers, providing biological inspiration to design recyclable materials. Elevated phosphorus content in velvet worm slime was previously observed and putatively ascribed to protein phosphorylation. Here, we show instead that phosphorus is primarily present as phosphonate moieties in the slime of distantly related velvet worm species. Using high-resolution nuclear magnetic resonance (NMR), natural abundance dynamic nuclear polarization (DNP), and mass spectrometry (MS), we demonstrate that 2-aminoethyl phosphonate (2-AEP) is associated with glycans linked to large slime proteins, while transcriptomic analyses confirm the expression of 2-AEP synthesizing enzymes in slime glands. The evolutionary conservation of this rare protein modification suggests an essential functional role of phosphonates in velvet worm slime and should stimulate further study of the function of this unusual chemical modification in nature.

The internal structure of the velvet worm projectile slime: A small-angle scattering study

ChemRxiv · 2022-11-07 · 1 citations

Velvet worms capture prey and defend themselves by ejecting an adhesive slime which has been established as a model system for recyclable complex liquids. Triggered by mechanical agitation, the sticky fluid rapidly transitions into solid fibers. The assembly of slime proteins into stiff polymers is fully reversible and recyclable enabling the recovery of the soluble precursors. In order to understand the rapid and reversible mechanoresponsive behavior of this material, here, we study the nanostructural organization of slime components using small-angle scattering with neutrons and x-rays under physiological native conditions, after drying and re-hydration, and mechanical agitation. The scattering intensities are successfully described with a three-component model accounting for proteins of two dominant molecular weight fractions and for protein-based nanoglobules with a radius of ~40-45 nm, which is in line with the literature. However, in contrast to the previous assumption that high molecular weight (HMW) proteins -- the presumed building blocks of the fiber core -- are contained in the nanoglobules, we find that the majority of slime proteins exist as free proteins in solution, including the HMW fiber core precursors. Only less than 10 % of the slime proteins are contained in the nanoglobules, necessitating a reassessment of the previously proposed function of nanoglobules in fiber formation. Exploiting distinct differences in the x-ray and neutron scattering contrast of slime re-hydrated with light and heavy water (D2O) indicates that the majority of lipids available in the slime are contained in the nanoglobules, where they are homogeneously distributed. Surprisingly, mechanical agitation of slime in a completely filled container causes gelification; however, this neither leads to fiber formation nor alters the bulk structure of the slime significantly, suggesting that interfacial phenomena and directional shearing are required for the formation of stiff fibers in velvet worm slime.

Comparative Animal Mucomics: Inspiration for Functional Materials from Ubiquitous and Understudied Biopolymers

ACS Biomaterials Science & Engineering · 2020 · 29 citations

• Computer Science
• Nanotechnology
• Biology

The functions of secreted animal mucuses are remarkably diverse and include lubricants, wet adhesives, protective barriers, and mineralizing agents. Although present in all animals, many open questions related to the hierarchical architectures, material properties, and genetics of mucus remain. Here, we summarize what is known about secreted mucus structure, describe the work of research groups throughout the world who are investigating various animal mucuses, and relate how these studies are revealing new mucus properties and the relationships between mucus hierarchical structure and hydrogel function. Finally, we call for a more systematic approach to studying animal mucuses so that data sets can be compared, omics-style, to address unanswered questions in the emerging field of mucomics. One major result that we anticipate from these efforts is design rules for creating new materials that are inspired by the structures and functions of animal mucuses.

Eastern Newt (<i>Notophthalmus viridescens</i>)

Wilderness and Environmental Medicine · 2020-12-17

The North America eastern newt (Notophthalmus viridescens) is commonly seen on hikes within the eastern United States and Canada.It has 3 life stages: an initial aquatic larva stage, a terrestrial red eft stage (Figure, left), and an aquatic adult stage (Figure ,right).The pictures included in this submission were taken at Sherando Lake Recreation Area (latitude 37.92 and longitude -79.01) within Virginia's Blue Ridge Mountains.The eastern newt is a larva for approximately 1 y before embarking on its terrestrial life stage.The terrestrial phase can last 3 y until the red eft

Two coastal Pacific evergreens, Arbutus menziesii, Pursh. and Quercus agrifolia, Née show little water stress during California's exceptional drought

PLoS ONE · 2020-04-02 · 10 citations

California's coastal climate is characterized by rainy winters followed by a dry summer season that is supplemented by frequent fog. While rising temperatures and drought caused massive tree mortality in central California during the 2011-2015 extreme drought, dying trees were less common in the central coast region. We hypothesized that cooler, maritime-ameliorated temperatures reduced the effects of drought stress on coastal vegetation. To test this, weekly measurements of water potential and stomatal conductance were made on two coast evergreen tree species, Arbutus menziesii and Quercus agrifolia, throughout the summer 2014 dry season. Water potential remained generally constant during this period but stomatal conductance declined in both species as the dry season progressed. Species' resistance to embolism was determined using the centrifuge method, and showed Q. agrifolia to be more vulnerable to embolism than A. menziesii. The stem vulnerability curves were consistent with species' seasonal water relations as well as their anatomy; the ring-porous Q. agrifolia had substantially larger conduits than the diffuse-porous A. menziesii. Leaf turgor loss points differed significantly as did other pressure-volume parameters but these data were consistent with the trees' seasonal water relations. Overall, the two species appear to employ differing water use strategies; A. menziesii is more profligate in its water use, while Q. agrifolia is more conservative, with a narrower safety margin against drought-induced loss of xylem transport capacity. Despite the extended drought, these species exhibited neither branch die-back nor any obvious symptoms of pronounced water-stress during the study period, implying that the maritime climate of California's central coast may buffer the local vegetation against the severe effects of prolonged drought.