Spider silk has extraordinary mechanical properties, displaying high tensile strength, elasticity, and toughness. Given the high performance of natural fibers, one of the long-term goals of the silk community is to manufacture large-scale synthetic spider silk. This process requires vast quantities of recombinant proteins for wet-spinning applications. Attempts to synthesize large amounts of native size recombinant spidroins in diverse cell types have been unsuccessful. In these studies, we design and express recombinant miniature black widow (Latrodectus hesperus) MaSp1 spidroins in bacteria that incorporate the NTD and CTD, along with varying numbers of codon-optimized internal block repeats. Following spidroin overexpression, we perform quantitative analysis of the bacterial proteome to identify proteins associated with spidroin synthesis. Nano-liquid chromatography with tandem mass spectrometry (nLC-MS/MS) reveals a list of molecular targets that are differentially expressed after enforced mini-spidroin production. This list included proteins involved in energy management, proteostasis, translation, cell wall biosynthesis and oxidative stress. Collectively, this study unveils new bacterial genes to target by genetic engineering to overcome bottlenecks that throttle spidroin overexpression in microorganisms.

Spider silk has outstanding mechanical properties, displaying high tensile strength and extensibility. The unique combination of strength and great extensibility make it one of the toughest materials in the world. Of the seven different spider silks, dragline silk, the lifeline silk of the spider, represents one of the most renowned fiber types that has extraordinary properties. As a result, many labs across the globe are racing to manufacture synthetic dragline silk fibers. With the production of synthetic dragline silk fibers, there are unlimited commercial applications. In this study, we developed several codon-optimized MaSp1 minifibroin constructs for recombinant protein expression in bacteria. These recombinant MaSp1 minifibroin constructs were engineered to contain the N-terminal domain (NTD), different copies of internal block repeats (ranging from 2 to 64 copies of 35 amino acid blocks), and the C-terminal domain (CTD). The NTD and CTDs were derived from the natural cDNA sequences of black widow spiders, while the internal block repeats were generated from synthetic DNA fragments that were codon-optimized for expression in Escherichia coli . Different numbers of internal block repeats were created using a specialized seamless cloning strategy. By applying this seamless cloning strategy, we successfully multimerized MaSp1 block repeats that approach the natural fibroin size. Moreover, through the construction of a customized NTD-CTD spidroin construct, multimerized block repeats from any fibroin can be rapidly inserted to facilitate minifibroin protein expression in bacteria. Overall, this strategy as well as the created vectors, should help advance the silk community in the production of synthetic silk fibers that have properties that more closely resemble natural fibers.