Applying structure and dynamics to modulate spider silk behaviour
Jan
K.
Rainey
Professor
Department
of
Biochemistry
&
Molecular
Biology,
Department
of
Chemistry,
and
School
of
Biomedical
Engineering
Dalhousie
University
Thursday,
August
4,
2022
10:30
a.m.
In-person: C2- 361 (Reading Room)
Online via MS Teams (please email Victoria Van Cappellen at vvancapp@uwaterloo.ca for access)
Abstract:
Female orb-weaving spiders produce up to seven silks for prey capture, locomotion, and protection from predators and the environment. Each fibrous silk is produced in a distinct gland from a different protein, with each having a distinctive combination of strength and extensibility enabling different biological functions. We have been focusing on two relatively poorly understood silks: wrapping (or aciniform) silk and pyriform silk. For both, we have developed efficient recombinant protein expression protocols and automated wet-spinning approaches to very consistently produce silk-like fibres that have tunable combinations of strength and extensibility. Using nuclear magnetic resonance (NMR) spectroscopy, we have evaluated atomic-level structuring and dynamics of these proteins in the soluble state and have probed the structural transitions that occur upon formation of an insoluble silk fibre. Both silks in their soluble form are modular series of helical bundles connected by a compact intrinsically disordered linker. Using clues from the solution-state backbone dynamics and stability of wrapping silk, we engineered a switchable version of wrapping silk through introduction of a disulfide bond that prevents fibre formation but which forms fibres of enhanced strength when this disulfide is reduced. Our structural data also allowed us to engineer a wrapping silk fusion protein that forms robust films that will sequester the protein nerve growth factor-b, enhancing nerve cell adhesion and neurite extension. The pyriform silk helical bundles are differ in architecture from those in wrapping silk, and both the structural transition upon fibre formation and the properties of resulting silk fibres appear distinct. With this information, pyriform silk is now also a prime candidate for rational biomaterials engineering. Our ongoing work is aims further detail the structural transition between soluble and fibrous states to understand these enigmatically high-performing materials and to apply this knowledge for the development of specifically tailored biomaterials.