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Modular peptides from the thermoplastic squid sucker ring teeth form amyloid-like cross–βsupramolecular networks

Research output: Contribution to journalArticle

Shu Hui Hiew, Paul A. Guerette, Ondrej J. Zvarec, Margaret Phillips, Feng Zhou, Haibin Su, Konstantin Pervushin, Brendan P. Orner, Ali Miserez

Original languageEnglish
JournalActa Biomaterialia
Early online date29 Sep 2016
DOIs
Publication statusE-pub ahead of print - 29 Sep 2016

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Abstract

The hard sucker ring teeth (SRT) from decapodiforme cephalopods, which are located inside the sucker cups lining the arms and tentacles of these squid species, have recently emerged as a unique model structure for biomimetic structural biopolymers. SRT are entirely composed of modular, block co-polymer-like proteins that self-assemble into a large supramolecular network. In order to unveil the molecular principles behind the SRT’s self-assembly and robustness, we describe a combinatorial screening assay that maps the molecular-scale interactions between the most abundant modular peptide blocks of suckerin proteins. By selecting prominent interaction hotspots from this assay, we identified four peptides that exhibited the strongest homo-peptidic interactions, and conducted further in-depth biophysical characterizations complemented by molecular dynamic (MD) simulations to investigate the nature of these interactions. Circular Dichroism (CD) revealed conformations that transitioned from semi-extended poly-proline II (PII) towards β-sheet structure. The peptides spontaneously self-assembled into microfibers enriched with cross β-structures, as evidenced by Fourier-Transform Infrared Spectroscopy (FTIR) and Congo red staining. NMR experiments identified the residues involved in the hydrogen-bonded network and demonstrated that these self-assembled β-sheet-based fibers exhibit high protection factors that bear resemblance to amyloids. The high stability of the β-sheet network and an amyloid-like model of fibril assembly were supported by MD simulations. The work sheds light on how Nature has evolved modular sequence design for the self-assembly of mechanically robust functional materials, and expands our biomolecular toolkit to prepare load-bearing biomaterials from protein-based block co-polymers and self-assembled peptides. [Statement of Significance] In recent years, the sucker ring teeth (SRT) located on the arms and tentacles of cephalopods have emerged as a very promising protein-based biopolymer with the potential to rival silk in biomedical and engineering applications. SRT are made of modular, block co-polymer like proteins (suckerins), which assemble into a semicrystalline polymer reinforced by nano-confined β-sheets, resulting in a supramolecular network with mechanical properties that match those of the strongest engineering polymers. In this study, we aimed to understand the molecular mechanisms behind SRT’s self-assembly and robustness. The most abundant modular peptidic blocks of suckerin proteins were studied by various spectroscopic methods. Using CD, FTIR and Congo red staining methods, we demonstrate that SRT peptides form amyloid-like cross-β structures.

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