Biophysical Society Thematic Meeting - October 25-30, 2015

Polymers and Self Assembly: From Biology to Nanomaterials

Tuesday Speaker Abstracts

Spider Silk Assembly is Mediated by a Lock and Trigger Mechanism Anna Rising Karolinska Institutet, Sweden No abstract

Development of Recombinant Spider Silk Proteins with Tunable Assembly Properties for Biomimetic Spinning Jan Johansson 1,2 , Anna Rising 1,2 . 1 Karolinska Institutet, Huddinge, Sweden, 2 SLU, Ultuna, Sweden. Spiders use specialized glands to make different types of protein-based silks with remarkable biochemical and mechanical properties, and artificial spider silk could be an ideal source for generation of novel high performance biomaterials. Spider silk fibres contain crystalline β-sheet regions, which mediate mechanical stability and that are formed within fractions of a second in the end of the spinning duct, but the soluble silk proteins (spidroins) can be stored at huge concentrations in the silk gland for long times, without aggregating prematurely. These properties have so far not been mimicked by recombinant spidroins. Spidroins contain unique repetitive segments, which determine the mechanical properties of the silk, as well as non- repetitive N- and C-terminal domains (NT and CT), which regulate conversion of the dope into fibres. We have studied the physiological regulation of spider silk formation and the molecular actions of NT and CT in detail. NT employs an evolutionarily conserved pH dependent three- step mechanism to decouple dimerization from locking of the dimer structure – a mechanism that ensures both rapid β-sheet aggregation and prevention of premature silk assembly. CT, in contrast, gets destabilised and converts into amyloid-like fibrils in a pH and CO2 dependent manner, a hitherto unique mechanism that we suggest is important for nucleating the formation of β-sheets in the silk fibres. We now use this knowledge to develop novel miniature spidroins with optimal properties in terms of solubility, yields upon recombinant production, and stability. A first generation of novel, designed minispidroins that show very high expression yields and solubility, and that can convert into fibres using a biomimetic spinning procedure have been generated. These minispidroins also allow high-resolution studies of spidroin structures in soluble and fibrillar states.

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