Structural components of spider silk are safely stored and assembled on demand with help from a molecular switch.

“Five times the tensile strength of steel and triple that of the
currently best synthetic fibers: Spider silk is a fascinating materialHow do spiders form long, highly stable and elastic fibers from the
spider silk s stored in the silk within split seconds?

“Spider silk consists of protein molecules, long chains comprising
thousands of amino-acid elements. X-ray structure analyses show that the
finished fiber has areas in which several protein chains are
interlinked via stable physical connections. These connections provide
the high stability. Between these connections are unlinked areas that
give the fibers their great elasticity.

“The situation within the silk gland is, however, very different: The
silk proteins are stored in high concentrations in an aqueous
environment, awaiting deployment. The areas responsible for interlinking
may not approach each other too closely; otherwise the proteins would
clump up instantaneously. Hence, these molecules must have some kind of
special storage configuration

“The protein chains are
stored with the polar areas on the outside and the hydrophobic parts of
the chain on the inside, ensuring good solubility in the aqueous

“When the protected proteins enter the spinning duct, they encounter
an environment with an entirely different salt concentration and
composition. This renders two salt bridges of the control domain
unstable, and the chain can unfold. Furthermore, the flow in the narrow
spinning duct results in strong shear forces. The long protein chains
are aligned in parallel, thus placing the areas responsible for
interlinking side by side. The stable spider silk fiber is formed.

“‘Our results have shown that the molecular switch we discovered at
the C-terminal end of the protein chain is decisive, both for safe
storage and for the fiber formation process,’ says Franz Hagn.” (Science Daily 2010)

Last Updated September 14, 2016