Modular peptides from the thermoplastic squid sucker ring teeth form amyloid-like cross-β supramolecular networks.
The hard sucker ring teeth (SRT) from decapodiforme cephalopods, which are located inside the sucker cups lining the arms and tentacles of these 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 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. Nuclear Magnetic Resonance (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.



The sucker ring teeth (SRT) located on the arms and tentacles of cephalopods represent 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, which demonstrate that SRT peptides form amyloid-like cross-β structures.
School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore 639798, Singapore; Center for Biomimetic Sensor Science (CBSS), NTU, Singapore 637553, Singapore.
Shu Hui
SH
Hiew
School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore 639798, Singapore; Center for Biomimetic Sensor Science (CBSS), NTU, Singapore 637553, Singapore; Energy Research Institute at Nanyang Technological University (ERI@N), 50 Nanyang Drive, Singapore 637553, Singapore.
Paul A
PA
Guerette
School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore 639798, Singapore; Center for Biomimetic Sensor Science (CBSS), NTU, Singapore 637553, Singapore.
Ondrej J
OJ
Zvarec
School of Biological Sciences, Nanyang Technological University, Singapore 639798, Singapore.
Margaret
M
Phillips
School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore 639798, Singapore.
Feng
F
Zhou
School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore 639798, Singapore.
Haibin
H
Su
School of Biological Sciences, Nanyang Technological University, Singapore 639798, Singapore.
Konstantin
K
Pervushin
School of Biomedical Sciences, King's College London, London SE1 1DB, United Kingdom.
Brendan P
BP
Orner
School of Materials Science and Engineering, Nanyang Technological University (NTU), Singapore 639798, Singapore; Center for Biomimetic Sensor Science (CBSS), NTU, Singapore 637553, Singapore. Electronic address: ali.miserez@ntu.edu.sg.
Ali
A
Miserez
D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D000818:Animals; D002942:Circular Dichroism; D049832:Decapodiformes; D000067493:Dynamic Light Scattering; D056004:Molecular Dynamics Simulation; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D066244:Proton Magnetic Resonance Spectroscopy; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014070:Tooth / Q000737:chemistry*
D000682:Amyloid; D019151:Peptide Library; D010455:Peptides
Amyloid; Beta-sheet; Peptide biomaterials; Self-assembly; Suckerins