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

Yu Suzuki,Tetsuo Asakura,Takanori Higashi,Takehiro K Sato,Takahiro Yamamoto,Hideyasu Okamura

doi:10.3390/molecules27020511

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.

Highlights

Silk protein is a promising resource in material science and medical applications because of its high biocompatibility, biodegradability, and excellent mechanical properties [1,2,3,4]
The spider dragline silk consists of two proteins, major ampullated spidroin 1 (MaSp1) and spidroin 2 (MaSp2) [25,32,33,48,49], which differ in the amino acid sequence
The structure and dynamics of recombinant spider silk protein (RSP) dissolved in formic acid (FA) were probed using solution NMR spectroscopy

Summary

Introduction

Silk protein is a promising resource in material science and medical applications because of its high biocompatibility, biodegradability, and excellent mechanical properties [1,2,3,4]. The sequential assignment of repetitive sequences containing polyAla and Gly-rich regions with 32-residue length was performed using various multidimensional NMR measurements, to obtain 1H, 13C, and 15N chemical shifts for each residue.

Results

Conclusion