In vivo effects of metal ions on conformation and mechanical performance of silkworm silks

• Published in: Biochimica et biophysica acta. General subjects Vol. 1861; no. 3; pp. 567 - 576
• Main Authors: Wang, Xin, Li, Yi, Liu, Qingsong, Chen, Quanmei, Xia, Qingyou, Zhao, Ping
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2017
• Subjects: Animals; Bombyx - metabolism; cations; Conformational transition; copper; Elastic Modulus; electrostatic interactions; fibroins; Fourier transform infrared spectroscopy; Internet; Ions - metabolism; Mechanical performance; mechanical properties; Metal ions; Metals - metabolism; modulus of elasticity; potassium; Protein Conformation, beta-Strand; silk; Silk - metabolism; Silk fiber formation; silkworms; β-Sheet; MSG; CD; V-ATPase; ICP-AAS; PSG; Mechanical performance; EST; qRT-PCR; SERCA; PDB; CDS; ASG; FTIR; Silk fiber formation; β-Sheet; NCBI; SEM; Metal ions; Conformational transition
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/j.bbagen.2016.11.025

The mechanism of silk fiber formation is of particular interest. Although in vitro evidence has shown that metal ions affect conformational transitions of silks, the in vivo effects of metal ions on silk conformations and mechanical performance are still unclear. This study explored the effects of metal ions on silk conformations and mechanical properties of silk fibers by adding K+ and Cu2+ into the silk fibroin solutions or injecting them into the silkworms. Aimed by CD analysis, FTIR analysis, and mechanical testing, the conformational and mechanical changes of the silks were estimated. By using BION Web Server, the interactions of K+ and N-terminal of silk fibroin were also simulated. We presented that K+ and Cu2+ induced the conformational transitions of silk fibroin by forming β-sheet structures. Moreover, the mechanical parameters of silk fibers, such as strength, toughness and Young's modulus, were also improved after K+ or Cu2+ injection. Using BION Web Server, we found that potassium ions may have strong electrostatic interactions with the negatively charged residues. We suggest that K+ and Cu2+ play crucial roles in the conformation and mechanical performances of silks and they are involved in the silk fiber formation in vivo. Our results are helpful for clarifying the mechanism of silk fiber formation, and provide insights for modifying the mechanical properties of silk fibers. [Display omitted] •Metal ions are essential for silk fiber formation in silkworm.•K+ and Cu2+ participate in fiber formation by forming β-sheet structures in silks.•K+ and Cu2+ can be used for improving the silk fibers mechanical properties.