Abstract

Spiders have evolved an arsenal of silk threads for various applications, using combinations of highly-repetitive silk proteins. These fibers have an extremely high range of tensile strength and elasticity, and along with their low immunogenicity, are desired by the military, medical, and fashion industries. However, spider silk farming is impractical, and alternatives are necessary for large-scale production. Inspired by nature’s design, we aim to engineer E. coli to produce genetically programmed synthetic fibers, and standardize the customization of their physical and functional properties. We have adapted Iterative Capped Assembly to modularize and flexibly control the assembly of silk domains that confer strength or elasticity in specific ratios. Varying the composition of the silk genes, or adding other functional proteins will allow precise fine-tuning of the resulting properties, and expand their practical utility. This platform can be readily applied to assemble other highly-repetitive proteins, or large genes from libraries of parts.