Conformation and dynamics of soluble repetitive domain elucidates the initial β-sheet formation of spider silk

July 30, 2019

Title

Conformation and dynamics of soluble repetitive domain elucidates the initial β-sheet formation of spider silk

Author

Nur Alia Oktaviani, Akimasa Matsugami, Ali D. Malay , Fumiaki Hayashi, David L. Kaplan, Keiji Numata

Year

2018

Journal

Nature Communications

Abstract

The β-sheet is the key structure underlying the excellent mechanical properties of spider silk. However, the comprehensive mechanism underlying β-sheet formation from soluble silk proteins during the transition into insoluble stable fibers has not been elucidated. Notably, the assembly of repetitive domains that dominate the length of the protein chains and structural features within the spun fibers has not been clarified. Here we determine the conformation and dynamics of the soluble precursor of the repetitive domain of spider silk using solutionstate NMR, far-UV circular dichroism and vibrational circular dichroism. The soluble repetitive domain contains two major populations: ~65% random coil and ~24% polyproline type II helix (PPII helix). The PPII helix conformation in the glycine-rich region is proposed as a soluble prefibrillar region that subsequently undergoes intramolecular interactions. These findings unravel the mechanism underlying the initial step of β-sheet formation, which is an extremely rapid process during spider silk assembly

Instrument

FVS-6000

Keywords

Vibrational circular dichorism, spider silk, β-sheet