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