Newly discovered protein makes spider silk super tough

A new gene that may explain the extraordinary toughness of Darwin’s bark spider silk is reported in a paper published this week in Communications Biology. This finding could have implications for engineering new biomaterials.

Darwin’s bark spider spins the largest known orb webs, suspended by threads up to 25 meters long. The dragline silk that the spider uses for creating the structural outline of the web is the toughest known biological material - 10 times tougher than Kevlar(R). But how the Darwin’s bark spider achieves this extreme toughness - a measure of both strength and extensibility - is unknown.

Jessica Garb and colleagues sequenced the genes expressed in the silk glands of Darwin’s bark spider and noticed an unusual silk gene. While the spider makes the major silk proteins known from other spiders, they also produce a protein with a unique repeated sequence. The sequence contains a large amount of proline, an amino acid known to make silk more stretchable. The authors suggest that this unique protein sequence is what makes the silk so tough.