Marine Structural Protein Stability Induced by Hofmeister Salt Annealing and Enzymatic Cross-Linking

• Published in: ACS biomaterials science & engineering 2020-10, Vol.6 (10), p.5519-5526
• Main Authors: Grant, Anise M, Krecker, Michelle C, Gupta, Maneesh K, Dennis, Patrick B, Crosby, Marquise G, Tsukruk, Vladimir V
• Format: Article
• Language: English
• Subjects: Animals; Characterization, Synthesis, and Modifications; Decapodiformes; Protein Conformation, beta-Strand; Protein Stability; Protein Structure, Secondary; Silk
• ISSN: 2373-9878; 2373-9878
• DOI: 10.1021/acsbiomaterials.0c00791

The Humboldt squid is one of the fiercest marine predators thanks in part to its sucker ring teeth that are biopolymer blends of a protein isoform family called suckerin with compression strength that rivals silkworm silk. Here, we focus on the popular suckerin-12 isoform to understand what makes the secondary structure of this biopolymer different in water and the potential role of diverse physical and chemical cross-linkings. By choosing a salt post-treatment, in accordance with the Hofmeister series, we achieved film stability with salt annealing that is comparable to chemical cross-links. By correlating the film morphology with the protein secondary structure changes, suckerin-12 films were shown to contract upon treatment with kosmotropic salts and exhibited increased stability in water. These changes are related to the rearrangement of suckerin-12 secondary structure from random coils and helices to β-sheets. Overall, understanding secondary structure changes caused by aqueous and ionic environments can be instructive for the tuning of the suckerin film sclerotization, its conversion to a tough biological material, and to ultimately produce the natural squid sucker ring teeth.