Molecules |  January 14, 2022

Presence of β-Turn Structure in Recombinant Spider Silk Dissolved in Formic Acid Revealed with NMR

Author:Yu Suzuki1,Takanori Higashi1,Takahiro Yamamoto1,Hideyasu Okamura1,Takehiro K. Sato2 and Tetsuo Asakura3

DOI:10.3390/molecules27020511

  • 1. Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui
  • 2. Spiber Inc.
  • 3. Department of Biotechnology, Tokyo University of Agriculture and Technology
Abstract Spider dragline silk is a biopolymer with excellent mechanical properties. The development of recombinant spider silk protein (RSP)-based materials with these properties is desirable. Formic acid (FA) is a spinning solvent for regenerated Bombyx mori silk fiber with excellent mechanical properties. To use FA as a spinning solvent for RSP with the sequence of major ampullate spider silk protein from Araneus diadematus, we determined the conformation of RSP in FA using solution NMR to determine the role of FA as a spinning solvent. We assigned 1H, 13C, and 15N chemical shifts to 32-residue repetitive sequences, including polyAla and Gly-rich regions of RSP. Chemical shift evaluation revealed that RSP is in mainly random coil conformation with partially type II β-turn structure in the Gly-Pro-Gly-X motifs of the Gly-rich region in FA, which was confirmed by the 15N NOE data. In addition, formylation at the Ser OH groups occurred in FA. Furthermore, we evaluated the conformation of the as-cast film of RSP dissolved in FA using solid-state NMR and found that β-sheet structure was predominantly formed.

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Spiber’s research initiatives into novel protein materials have benefited from grants and subsidies from Tsuruoka City, Yamagata Prefecture, and Japan’s ImPACT program.