Notes

The protein, ADF3 is the principle component of the dragline silk produced by the orb-weaver spider (Araneus diadematus). Spiders produce a number of different kinds of silks for different purposes - to be strong, sticky, elastic, etc. Produced by an organ called the ampullate major, dragline silks are the strong structural silks used for the outer rim and spokes of a web, as well as the dragline for the spider.

ADF3 is a large, repetitive, hydrophobic protein that polymerizes into a macroscopic silk. Long repeats of alanine, glycine and serine allow the silk to become insoluble after being produced.[1] The repeats form β-sheets that stack parallel to the fiber axis leading to the silk’s famous high-tinsel strength.[2]

A number of companies have been formed to produce spider silk commercially. In general it has not been economical to use harvest silk from spiders themselves, and so the DNA that encodes for proteins like ADF3 has been transformed into other organisms like goats, yeast, and E. coli. Last year Bolt Threads raised $50 million and partnered with Patagonia to mass produce commercial quantities of its spider silk in yeast. Spiber, another company has produced a Moon Parka made from its spider silk in cooperation with North Face. AMSilk partnered with Adidas to produce a biodegradable shoe made from its spider silk.

Many of the fabrics we interact with daily are either complex sugars produced by plants (cotton), or derived from petrolium products (nylon). Uniquely, spider silk is produced industrially in fermenters much like beer. The silk components are produced by brewing yeast in an ecologically friendly manufacturing process that uses as its ingredients, water, sugar and heat.

Looking to the future, because the commercial silks all are produced from a known amino acid sequence, by rationally altering that sequence new products with new properties can be rapidly developed. Silks can be made more or less water resistant, elastic, or of different colors all by flipping a few bits in the DNA used to produce it.

Companies

• Bolt Threads in California produces silk in yeast.
• Spiber a Japanese company produces its silk in E. Coli.
• AMSilk a German company produces its silk in E. Coli.

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1. Huemmerich et al. 2004
2. Parkhe et al. 1997