Spider attachrnentdisc silk fibers are spun into a viscous liquid that rapidly solidifies, gluing dragline silk fibers to substrates for locomotion or web construction. Here we report the identification and artificial spinning of a novel attachment disc glue silk fibroin, Pyriform Spidroin 2 (PySp2), from the golden orb weaver Nephila c/avipes. MS studies support PySp2 is a constituent of the pyriform gland that is spun into attachment discs. Analysis of the PySp2 protein architecture reveals sequence divergence relative to the other silk family members, including the cob weaver glue silk fibroin PySpl. PySp2 contains internal block repeats that consist of two sub-repeat units: one dominated by Ser, Gin and Ala, the other Pro-rich. Artificial spinning of recombinant PySp2 truncations shows that the Ser-Gln-Ala-rich sub-repeat is sufficient for the assembly of polymeric subunits and subsequent fiber formation. These studies support that both orb- and cob-weaving spiders have evolved highly polar block-repeat sequence with the ability to self-assemble into fibers, suggesting a strategy to allow fiber fabrication in the liquid environment of the attachment discs.

Spider silk is renowned for its extraordinary mechanical properties, having a balance of high tensile strength and extensibility. To date, the majority of studies have focused on the production of dragline silks from synthetic spider silk gene products. Here we report the first mechanical analysis of synthetic egg case silk fibers spun from the Latrodectus hesperus tubuliform silk proteins, TuSp1 and ECP-2. We provide evidence that recombinant ECP-2 proteins can be spun into fibers that display mechanical properties similar to other synthetic spider silks. We also demonstrate that silks spun from recombinant thioredoxin-TuSp 1 fusion proteins that contain the conserved C-terminal domain exhibit increased extensibility and toughness when compared to the identical fibers spun from fusion proteins lacking the C-terminus. Mechanical analyses reveal that the properties of synthetic tubuliform silks can be modulated by altering the post-spin draw ratios of the fibers . Fibers subject to increased draw ratios showed elevated tensile strength and decreased extensibility, but maintained constant toughness. Wide-angle X-ray diffraction studies indicate that post-drawn fibers containing the Cterminal domain of TuSp 1 have more amorphous content when compared to fibers lacking the C-terminus. Taken together, these studies demonstrate that recombinant tubuliform spidroins that contain the conserved C-terminal domain with embedded protein tags can be effectively spun into fibers, resulting in similar tensile strength but increased extensibility relative to non-tagged recombinant dragline silk proteins spun from equivalently sized proteins.