Major structural protein in locust mandible capable of forming extraordinarily stiff materials via hierarchical self-assembly

Summary

Locust mandibles have stiff cuticles to process rough food. Therefore, the mandible is a reservoir of stiff structural proteins (SPs). Here, LmCPH-1, the most abundant SP in locust mandibles, is reported to be an indispensable stiff SP in mandibles. In vivo, suppression of LmCPH-1 expression seriously weakens the mechanical properties of the mandible. In vitro, LmCPH-1 undergoes hierarchical self-assembly to form a film with an ultrahigh modulus (12 GPa), which outperforms most protein-based materials. The stiffness of LmCPH-1 film can be attributed to its high β-sheet/β-crystal content formed through self-assembly. Molecular dynamics simulations indicate that the C-terminal region of LmCPH-1 plays a vital role in its self-assembly process. We conclude that LmCPH-1 strengthens the locust mandible by forming a stiff cement to fill the chitin scaffold. The findings not only represent a universal reinforcing mechanism of insect cuticle but also provide a potent starting material for sustainable materials.